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TRANSACTIONS 



OF THE 



KOYAL SOCIETY OF EDINBUKGH. 



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32. 



TRANSACTIONS 



OF THE 



ROYAL SOCIETY 



OF 



EDINBURGH. 



VOL. XXXII. 




EDINBURGH: 

PUBLISHED BY ROBERT GRANT. & SON, 107 PRINCES STREET, 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON. 



MDCCCLXXXVII. 



Part I. published ... Dec. 3, 1883. 

Part II. ... Nov. 29, 1884. 

Part III. „ ... Feb. 13, 1886. 

Part IV. „ ... July 9, 1887. 



CONTENTS. 



VI. The Elementary Composition of Nitroglycerine. By Matthew 
Hay, M.D., and Okme Masson, M.A., B.Sc, . 

VII. Report on the Tunicata collected during the Cruise of H.M.S, 
" Triton " in the Summer of 1882. By W. A. Herdman, D.Sc. 
Professor of Natural History in University College, Liverpool 
(Plates XVI.-XX.), . . . . " . ' 



PAGE 



PART I. (1882-83.) 

I. The Pycnogonida dredged in the Faroe Channel during the Cruise 
of H.M.S. " Triton " (in August 1882). By Dr P. P. C. Hoek, 
Member of the Royal Academy of Science of the Netherlands. 
(Plate L), ... 1 

II. Bright Clouds on a Bark Night Sky. By Professor C. Piazzi Smyth, 

Astronomer-Royal for Scotland. (Plates II.-XIV.), . 11 

III. Note on the Little b Group of Lines in the Solar Spectrum and the 

New College Spectroscope. By C. Piazzi Smyth, Astronomer- 
Royal for Scotland. (Plate XV.), . . . .37 

IV. Observations on the Annual and Monthly Growth of Wood in 

Deciduous and Evergreen Trees. By the late Sir Robert 
Christison, Bart., and Dr Christison, . . . .45 

V. A Contribution to the Chemistry of Nitroglycerine. By Matthew 
Hay, M.D., Assistant to the Professor of Materia Medica in 
the University of Edinburgh, . . . . .67 



78 



93 



VIII. Report on the Pennatulida dredged by H.M.S. " Triton" By A. 
Milnes Marshall, M.D., D.Sc, M.A., Fellow of St John's 
College, Beyer Professor of Zoology in Owens College. (Plates 
XXI.-XXV.), . . . . . .119 



VI CONTENTS. 



IX. Aster oidea dredged in the Faeroe Channel during the Cruise of 
H.M.S. "Trito?i" in August 1882. By W. Percy Sladen, 
F.L.S., F.G.S. Communicated by John Murray, F.R.S.E. 
(Plate XXVI), . 153 

X. On a New Species of Pentastomum (P. protelis) from the Mesentery 
of Proteles cristatus ; with an Account of its Anatomy. By 
W. E. Hoyle, M.A. (Oxon.), M.R.C.S., Naturalist to the 
"Challenger" Commission. (Plates XXVIL, XXVIIL), 165 

XL On Superposed Magnetisms in Iron and Nickel. By Professor 

C. G. Knott, D.Sc. (Plate XXIX.), . ' . . .193 

XII. On the Relative Electro- Chemical Positions of Wrought Iron, Steels, 
Cast Metal, <%c, in Sea Water and other Solutions. By Thomas 
Andrews, A.M., Inst. C.E., F.C.S. (Plates XXX.-XXXIV.), 204 



PART II. (1883-84.) 

XIII. Report on the Tnnicata dredged during the Cruises of H.M.SS. 
" Porcupine " and " Lightning " in the Summers of the Years 
1868, 1869, and 1870. By Professor Herdman, F.R.S.E. 
(Plates XXXV., XXXVL), 219 

XIV. Note on Sir David Brewster's Line Y in the Infra-Red of the Solar 
Spectrum. By Professor Piazzi Smyth, F.R.S.E., Astronomer- 
Royal for Scotland. (Plate XXXVIL), , t . . 233 

XV. On the Formation of Small Clear Spaces in Dusty Air. By John 

Aitken, F.R.S.E. (Plate XXXVIII.), . .239 

XVI. On Stichocotyle Nephropis, a New Trematode. By J. T. Cun- 

ningham, B.A. (Plate XXXIX.), . . . .273 

XVII. The Enumeration, Description, and Construction of Knots of 

fewer than Ten Crossings. By Rev. T. P. Kirkman, F.R.S. 
(Plates XL.-XLIIL), 281 



CONTENTS. vii 



XVIII. On the Approximation to the Roots of Cubic Equations by help 
of Recurring Chain-Fractions. By Edward Sang, LL.D., 
F.E.S.E, 311 

XIX. On Knots. Part II. By Professor Tait, Sec. E.S.E. (Plate 

XLIV.), 327 

Appendix. — Note on a Problem in Partitions. By Professor 
Tait, Sec. E.S.E., ...... 340 

XX. On the Philosophy of Language. By Emeritus Professor 

Blackie, F.E.S.E., . . . . . . 343 

XXI. The Old Red Sandstone Volcanic Rocks of Shetland. By 
B. N. Peach, F.E.S.E., and John Horne, F.E.S.E. (Plates 
XLV, XL VI.), 359 

XXII. Observations on a Green Sun and Associated Phenomena. By 

Professor C. Michie Smith, F.E.S.E. (Plate XLVII), . 389 

XXIII. An Example of the Method of Deducing a Surface from a Plane 
Figure. By Professor L. Cremona, LL.D. Edin., Hon. 
F.E.SS. Lond. and Edin., . . . . .411 



PAET III. (1884-85.) 

XXIV. Micrometrical Measures of Gaseous Spectra under High Dis- 
persion. By Professor C. Piazzi Smyth, F.E.S.E., and Astro- 
nomer-Eoyal for Scotland. (Plates XLVIII.-LXXVIIL), 415 

XXV. On Bipartite Functions. By Thomas Muir, LL.D., . .461 

XXVI. The 364 Unifilar Knots of Ten Crossings, Enumerated and 

Described. By Eev. Thomas P. Kirkman, M.A., F.E.S, . 483 

XXVII. On Knots. Part III. By Professor Tait. (Plates LXXIX.- 

LXXXL), . . . . . .493 

XXVIII. A New Graphic Analysis of the Kinematics of Mechanisms. 
By Professor Eobert H. Smith, Mason College, Birming- 
ham. (Plate LXXXIL), . . . . .507 



Vlll CONTENTS. 

PAGE 

XXIX. The Visual, Grating and Glass-lens, Solar Spectrum (in 1884). 
By Professor C. Piazzi Smyth, F.K.S.E., and Astronomer- 
Royal for Scotland. (Plates LXXXIII.-CXLIIL), . 519 

XXX. Observations on the Recent Calcareous Formations of the 
Solomon Group made during 1882-84. By H. B. Guppy, 
M.B., F.G.S., Surgeon H.M.S. "Lark." Communicated by 
John Murray, Ph.D. (Plates CXLIV., CXLV.), . 545 

XXXI. Observations on Atmospheric Electricity. By Professor C. 

Michie Smith. (Plate CXLVL), . . . .583 

XXXII. Note on Ectocarpus. By John Rattray, M.A., B.Sc, Scottish 
Marine Station, Granton, Edinburgh. Communicated by 
John Murray, Ph.D. (Plates CXLVIL, CXLVIIL), . 589 

XXXIII. Anatomy and Physiology of Patella vulgata. Part I. Ana- 

tomy. By R. J. Harvey Gibson, M. A. Communicated by 
Professor Herdman, D.Sc. (Plates CXLIX.-CLIIL), . 601 

XXXIV. Detached Theorems on Circidants. By Thomas Muir, LL.D., 639 
XXXV. On the Hessian. By Professor Chrystal, . . . 645 



Appendix — 

The Council of the Society, . 654 

Alphabetical List of the Ordinary Fellows, . . . 655 

List of Honorary Fellows, . . . . . .668 

List of Ordinary Fellows Elected during Sessions 1883-85, . 674 

Laws of the Society, ...... 681 

The Keith, Brisbane, and Neill Prizes, .... 688 

Awards of the Keith, Makdougall-Brisbane, and Neill Prizes, . 690 

Proceedings of the Statutory General Meetings, . . . 693 

List of Public Institutions and Individuals entitled to receive Copies 

of the Proceedings and Transactions, . . .701 

Index, ........ 707 



TRANSACTIONS 



6P THE 



ROYAL SOCIETY OF EDINBURGH 

VOL. XXXII. PART I.— FOR THE SESSION 1882-83. 



CONTENTS. 



Page 
Art. I. — The Pycnogonida dredged in the Farce Channel during the Cruise of H.M.S. 
"Triton" (in August 1882). By Dr P. P. C. Hoek, Member of the Eoyal 
Academy of Science of the Netherlands. (Plate I.), ., . . 1 

II. — Bright Clouds on a Dark Night Sky. By C. Piazzi Smyth, Astronomer-Eoyal for 

Scotland. (Plates II. to XIV.), . . . . . .11 

III. — Note on the Little b Group of Lines in the Solar Spectrum and the new College 
Spectroscope. By C. Piazzi Smyth, Astronomer - Eoyal for Scotland 
(Plate XV.), 37 



IV. — Observations on the Annual and Monthly Growth of Wood in Deciduous and Ever 
green Trees. By the late Sir Eobebt Christison, Bart., and Dr Christison, 

V. — A Contribution to the Chemistry of Nitroglycerine. By Matthew Hay, M.D. 
Assistant to the Professor of Materia Medica in the University of Edinburgh, 



45 



67 



VI. — The Elementary Composition <of Nitroglycerine. By Matthew Hay, M.D., and 

Orme Masson, M.A., B.Sc, . ... . . . .78 

VII. — Report on the Tunicata collected during the Cruise of H.M.S. "Triton" in the 
Summer of 1882. By W. A. Herdman, D.Sc, Professor of Natural History 
in University College, Liverpool. (Plates XVI. to XX.), . . .93 

VIII. — Report on the Pennatidida dredged by H.M.S. " Triton." By. A Milnes Marshall, 
M.D., D.Sc, M.A., Fellow of St John's College, Beyer Professor of Zoology in 
Owens College. (Plates XXI. to XXV.), . . . . .119 

IX. — Asteroidea dredged in the Faeroe Channel during the Cruise of H.M.S. " Triton " 
in August 1882. By W. Percy Sladen, F.L.S., F.G.S. Communicated by 
John Murray, F.E.S.E. (Plate XXVI.), . . . . .153 

[For remainder of Contents, see last page of Cover. ] 




TKANSACTIONS. 



I. — The Pycnogonida dredged in the Faroe Channel during the Cruise of H. M.S. 
" Triton " (in August 1 882). By Dr P. P. C. Hoek, Member of the Boyal 
Academy of Science of the Netherlands. (Plate I.) 

(Communicated by Mr John Murray. ) 

During the cruise of H.M.S. " Triton" a small but very interesting collec- 
tion of Pycnogonids was made. Mr John Murray sent it over to me, and 
asked me to prepare a report on it, which I gladly undertook to do. 

The thirteen stations of the "Triton" cruise are situated about 60° lat. 
north, and between 6° and 9° 6' long, west of Greenwich. At six of these 
stations Pycnogonids were obtained. The depth of the sea at these stations 
varies from 433 to 640 fathoms; at two of them the bottom was hard 
ground or stones, at three the bottom was mud, at one ooze. At three of the 
stations the bottom temperature was about 45°, at the three others about 30°. 
The first three being in the so-called warm area, the latter in the cold area. 

The number of species collected amounts to eleven. Three of them inhabit 
the cold area, and were not found in the warm area [Nymplion Strbmii, Kroyer; 
Colossendeis proboscidea, Sab. spec. ; and C. angusta, G. O. Sars) ; five species 
were observed only in the warm area {Nymplion hirtipes, Bell ; N. macrum, 
Wilson ; N. longitarse, Kroyer ; Pallene malleolata, G. O. Sars ; Pallenopsis 
tritonis, n. sp.) . The remaining three seem to inhabit the cold as well as the 
warm area. Nymplion macronyx, G. O. Sars, however, is represented by several 
hundred specimens from the cold area, and by one specimen only from the 
warm area ; and this is also the case with Nymplion robustum, Bell. Of both 
species the number of specimens collected at stations in the cold area was so 
large, that the occurrence of one specimen at a station in the warm area 
seems rather unimportant — it must be considered as a specimen which has got 
astray ; but whether this happened before or after its being dredged, I cannot 
say with certainty. As in both instances the station in the warm area 
from which the single specimen was obtained follows one in the cold area, 

VOL. XXXII. PART I. A 



2 DR P. P. C. HOEK ON THE 

at which several hundred specimens of the one, and upwards of fifty of the 
other, species were collected, it is even probable that — the same fishing appara- 
tus (trawl) being used — one specimen was overlooked either remaining between 
the meshes of the trawl or clinging to the rope. The nature of the animals, 
with their long and numerous legs, each furnished with a claw, favours this 
suggestion. The only specimen which remains as inhabiting both areas is 
Nymphon grossipes, Oth. Fabr. : it is represented by eight specimens, four of 
which are from the cold water area, and four from the warm water area. 

Comparing these facts with those furnished by the cruise of the " Knight 
Errant" (1880), of the " Voringen " (1876 and 77-78), and of the " Willem 
Barents " (1878 and 1879), and also with what is known about the Pycnogonids 
of the North American coast (for which knowledge we are much indebted to 
the studies of Mr E. B. Wilson), we have made the following table, from 
which those species are excluded which have hitherto been only once 
observed : — 



Name of the Species. 


Area in which 

H. M.S. 'Triton' 

caught it. 


Area in which 

the 

'KnightErraut' 

caught it. 


Area in which 
G. 0. Sars 
caught it. 


Does it 

inhabit the 
Arctic Sea ? 


Does it 
inhabit the 
Atlantic near 
the N. Ameri- 
can coast ? 


Nymphon rdbustum, Bell, 


Cold 


Cold 


Cold 


Yes 


No 


„ macronyx, G. G. Sars, . 


Cold 


Cold 


Cold 


? 


No 


„ Stromii, Kroyer, . 


Cold 


Both 


Cold 


Yes 


Yes 


„ hirtipes, Bell, 


Warm 


... 


Cold 


Yes 


Yes 


„ macrum, Wilson, . 


Warm 






No 


Yes 


„ longitarse, Kroyer, 


Warm 




Warm 


Yes 


Yes 


„ grossipes, Oth. Fabr., 


Both 


Cold 


Cold 


Yes 


Yes 


„ serratum, G. 0. Sars, . 






Beth 


Yes 


No 


Colossendeis proboscidea, Sab. spec, 


Cold 


Cold 


Cold 


Yes 


No 


„ angusta, G. 0. Sars, . 


Cold 




Cold 


7 


Yes 


I'allene malleolata, G. 0. Sars, 


Warm 




Both 


2 


No 


Pallenopsis tritonis, n. sp., 


Warm 






No 


Probably 



From this table the following conclusions may be deduced : — 

1. The species which inhabit the cold area in the Atlantic occur also in the 
Arctic Ocean (N. robustum, C. pi'oboscidea) ; those which have notyet been observed 
in the Arctic may be expected to be found there (N. macronyx, C. angusta). 
They are not found near the American coast, or only at a very considerable 
depth (Colossendeis angusta at a depth from 810 to 1242 fathoms). 



PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. "TRITON." 3 

2. The species which inhabit the warm area in the Atlantic occur also at a 
much lower latitude near the American coast (N. macrum, Pallenopsis, spec). 
They are not found in the Arctic Ocean. 

3. The species which inhabit both areas in the Atlantic occur in the Arctic 
Ocean as well as near the American coast (N. Strbmii, N. hirtipes, N. grossipes). 
Nymphon serratum inhabits both areas in the Atlantic ; it has been observed in 
the Arctic, and will probably be found at a much lower latitude. Pallene 
malleolata inhabits both areas also, and will probably be found to have a wide 
northern as well as southern distribution. 

4. The only species whose distribution does not seem to be in accordance with 
the temperature of the water it inhabits is N. longitarse. Hitherto it has only 
been observed in the warm water area, yet it inhabits the Arctic as well as the 
New England coast. However, I think this exception is of no consequence : 
in the first place, because it always, in the northern parts of the Atlantic at 
least, lives rather solitary, and therefore may be found in the future in the cold 
area also ; and in the second place, because it is a somewhat uncertain species, 
and perhaps will turn out to be a variety of N. grossipes. 

A few notes on the species submitted to my examination are appended 
here : — 

1. Nymphon robustum, Bell. 

A very large number of specimens of this species was obtained at 
Stations 8 and 9, fourteen specimens were dredged at Station 6, and one specimen 
was taken from the bottle which contained the Pycnogonids of Station No. 10. 
The specimens show the same difference with those of higher northern latitudes 
as do those dredged by the " Knight Errant " in 1880 ; they are not nearly so 
stout, and are smaller. Numerous specimens had attached to the legs a Scal- 
pellum, for which I proposed the name Scalpellum nymphocola. It is a 
curious fact, that the specimens of the Barents Sea (and I studied also those of 
the third and fourth cruise of the Dutch schooner "Willem Barents") never 
had this Cirriped on their legs. 

2. Nymphon hirtipes, Bell. 

Only one small specimen of this species was dredged at Station No. 5. Mr 
Edmund B. Wilson and Professor G. O. Sars apply to this species the name N. 
hirtum, Fabr. But the description of Fabricius {Entom. System., 1794) is not 
only very brief, but it is totally insufficient to recognise the species. The 
species which Kroyer (1845) described under the name N. hirtum, Fabr., no 
doubt differs from the present species (as is stated by Professor Sars and by 



4 DR P. P. C. HOEK ON THE 

Wilson also). I therefore retain the name of Fabricius for Kroyer's species, 
the first that has been described recognisable under that name, and I give to 
the other the name of Bell, whose figures and description doubtless refer to it. 
Although this species is common in high northern latitudes (Bell, Miers, 
Hoek), it seems to be rather scarce in the North Atlantic (Professor G. O. Sars 
only observed it once ; it was not obtained by the " Knight Errant"; and the 
" Triton " collected only one specimen). Off Halifax it was taken in great num- 
bers by the U.S. Fish Commission in 1877 (Wilson). 

3. Nymphon Stromii, Kroyer. 

During the cruise of H.M.S. "Triton" this species was met with on three 
different occasions. At Station 9 about forty specimens of it were taken ; 
at Station 8, three, aud at Station 6, one specimen. It was not observed at 
one of the stations of the warm area, as happened during the cruise of the 
"Knight Errant." 

4. Nymphon macronyx, G. O. Sars. 

This species was first observed by Professor Sars during the first cruise of 
the " Voringen" (1876); it was again collected in the Faroe Channel during the 
summer of 1880 ("Knight Errant") ; and it is now dredged for the third time 
by H.M.S. "Triton." Professor Sars collected four specimens; the "Knight 
Errant " took about thirty specimens ; and the " Triton " several hundreds. 
These specimens were obtained in about lat. 60° north, whereas Sars got his 
specimens at 62° 44' 5". Whether its distribution will be found to extend still 
further north, I cannot say with certainty. I only think it very probable, as 
this species is an inhabitant of the cold area. 

At Station 8, several hundred specimens of this species were taken, 
„ 9, about fifty specimens „ „ 

w 6, „ two „ „ „ 

and one specimen (see p. 1) was found in the bottle containing the Pycno- 
gonids from Station 10. 

One of the specimens of Station 8 has no eyes ; or, better perhaps, has no 
pigment in its eyes. 

."). Nymphon macrum, Wilson. 

Wilson, Pycnogonida of New England, Report U.S. Commission of Fish and Fisheries, vi. 

(1878), 1881, p. 487, pi. iv., figs. 21-23. 
Syn. Nymphon brevicollnm, Hoek, Report "Challenger" Pycnogonida, 1881, p. 45, pi. iii. 

figs. 13-15; pis. xv. figs. 12 and 13. 

The general appearance of this species is much like N. Stromii. When 
studying the details as to the length of the joints of the palpi, of the tarsal joints 



PYCNOGONIDA DREDGED DURING THE CRUISE OE H.M.S. "TRITON." 5 

of the legs, the structure of the first segment of the body, of the oculiferous 
tubercle, &c, it is, however, easily distinguished not only from the above named, 
but also from other species of the genus. 

The eggs of N. Strbmii are small and very numerous ; those of A T . macrum 
are very large, each egg-mass containing a few eggs only. 

This species inhabits the warm water area. Four specimens were collected 
at Station 10 ; nineteen specimens at Station 11. 

The U.S. Fish Commission took this species at a few localities in the Gulf 
of Maine, in from 85 to 115 fathoms; the " Challenger " south of Halifax, in 83 
fathoms. The depth at which it was collected during the cruise of H.M.S. 
" Triton " was between 516 and 555 fathoms. 

6. Nymphon grossipes, Oth. Fabr. 

In all, eight specimens which I refer to this species were collected. In 
most of its characters this species is very variable ; its conical and acutely 
pointed oculiferous tubercle, the length of the third joint of the palpus, which 
is longer than the second joint, and the armature of the second tarsal joint of 
the leg, are, I think, the best marks for its distinction. 

Hitherto, this species was, in the Northern Atlantic, only observed in the 
cold area. H.M.S. " Triton " collected four specimens in the warm and four in 
the cold area, viz., three at Station 6, one at Station 9, and four at Station 10. 

7. Nymphon longitarse, Kroyer. 

At Station 11, at a depth of 555 fathoms, two specimens of this species were 
dredged. They are very small specimens, having an extremely attenuated 
appearance, with blunt oculiferous tubercles, and with the first tarsal joint 
twice as long as the second. 

8. Colossendeis proboscidea, Sab. spec. 

This robust species is represented by a single specimen taken at Station 9, 
at a depth of 608 fathoms. For a figure of this species I refer to my paper on 
the Pycnogonids of the " Willem Barents." 

9. Colossendeis angusta, G. 0. Sars. 

G. O. Sars, Prodromus descriptionis, Arch, for Math, og Naturv., ii. p. 268, 1877. 

(Plate I. fig. 8.) 

This species is known from a short (Latin) description by Professor G. O. 
Sars. Mr Wilson {Bull. Mus. Comp. Zool., viii. 1881, p. 243) got specimens of 
what he believes to be the same species from deep water in the Atlantic, 
between N. lat. 38° and 41°, and W. long. 65° and 73°, and points out several 
differences of greater or less importance between his specimens and those of 
Sars. 



6 DR P. P. C. HOEK ON THE 

Some of these differences may be due to variation of the species, the others 
to the provisional character of the paper of Professor Sars. Nor would I have 
insisted upon this disagreement had not the specimens collected with H.M.S. 
" Triton " shown also some of the variations from the description of Sars pointed 
out by Wilson. 

The largest specimen collected by the " Triton " measures 20 mm. ; the 
proboscis, which is slightly swollen a little behind the middle, is not quite 
10 mm. The abdomen, according to Sars and Wilson, is one-third the length 
of the trunk ; in the " Triton " specimens, however, it is Only one-fourth that 
length. The third (second, Sars) joint of the palpus is a great deal longer than 
the fifth (fourth, Sars). The eighth joint of the palpus is globose, and much 
shorter than the two last. The claw of the ovigerous leg is not confluent with 
the last joint (Sars) : in my specimens, as in those of Wilson, there is a distinct 
articulation between them. The colour of the specimens is beautiful orange. 

There are in all eight specimens. Of these five are from 16 to 20 mm., and 
about, or quite, full grown. The three other specimens measure from 9 to 
12 mm., and are furnished with very slender and three-jointed mandibles (fig. 8). 
The last joint of these mandibles terminate in minute rudimentary chelae. 

I observed the same in a young male specimen of Colossendeis gracilis 
collected during the cruise of H.M.S. " Challenger" [vide Report " Challenger " 
Pycnogonida, p. 69). It is a very curious fact that some of the species of 
the genus Colossendeis retain a pair of appendices of the larval state almost 
till the animal has reached the size of the adult ; and these appendices do 
not remain in the extremely small and feeble condition of larval life, but 
grow with the proboscis till the length of this part of the body surpasses half 
its length when full grown. Probably the mandibles are only lost when the 
animal comes to maturity. 

This species is an inhabitant of the cold water area ; the highest latitude 
at which it has been observed is 63° 10' 2" : it has not been found as yet in 
the Arctic region. Sars obtained it from 417, the "Triton" from 466 to 640 
fathoms. Off the eastern coast of the United States Mr Agassiz has dredged 
it at a depth of from 810 to 1242 fathoms — a striking instance of the southward 
extension of Arctic forms in deep water, as Mr Wilson says ; for though it has 
not been found in the Arctic Ocean as yet, we may safely conclude, from its 
occurrence in the cold water area, that hereafter it will be met with there. 

Seven specimens were taken at Station No. 8 and one at Station No. 6. 

10. Pallme malleolata, G. O. Sars. 

G. O. Sars, Crustacea et Pycnogonida nova, Arch, for Math, og Naturv., iv. p. 469, 1879. 

(Plate I. fig. 7.) 
I know this species only from the description of Professor G. O. Sars. 



PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S "TRITON. 7 

Four robust specimens were taken at Station No. 10 at a depth of 516 
fathoms. It is the only representative of the genus found at a considerable depth 
in high northern latitudes. Professor Sars collected it between N. lat. 72° 
27' and 80°; the station at which the "Triton" dredged it is N. lat. 59° 39' 30", 
in the warm area. 

11. Pallenopsis tritonis, n. sp. 

(Plate I. figs. 1-6.) 

Animal slender, the lateral processes, at the end of which the legs are 
inserted, being distinctly separated from each other. Dark yellow coloured, 
smooth : no tubercles or hairs are visible on the surface of the body even when 
studied with a lens. Legs not very hairy ; the structure of the hairs, as in 
numerous species of Pallene and Pallenopsis, furnished with small barbs 
pointing towards the tip. 

Proboscis nearly cylindrical, slightly swollen a little behind the middle. 
Mouth large, as in the other species of the genus {Pallenopsis oscitans, Hoek, 
spec. &c). The length of the proboscis is not quite equal to that of the 
oculiferous and two succeeding segments taken together. 

Oculiferous segment longer than the two following taken together, somewhat 
swollen in front, where it overhangs the base of the proboscis, and where it is 
furnished with the rounded oculiferous tubercle. Of the eyes the two anterior 
ones have very large clear lenses ; the other two are a great deal smaller and 
are placed at the back side of the tubercle, a dark reddish and rhombiform 
pigment spot being placed at the tip of the tubercle. 

The form of the other segments is the same as in other species of the 
genus : the abdomen is cylindrical, its length corresponds with that of the 
second and third segments taken together (fig. 1). 

The mandibles are very slender, the two basal joints extend beyond the 
tip of the rostrum, third joint considerably swollen, with the claws curved and 
not so long as in P. longirostris, Wilson (fig. 2). 

The palpi are represented by very small globular knobs implanted laterally 
near the base of the proboscis. 

The ovigerous legs (figs. 3 and 4) have the first joint almost globular, the 
second, fourth, and fifth joints of considerable and nearly equal length, the 
third a great deal longer than the first, and also a little longer than the sixth 
joint, which is swollen at the distal extremity. Seventh to tenth joints gradually 
diminishing in length, and at the same time growing more slender. Tenth joint 
rather elongate. Joints first to fifth are sparsely hairy, joints sixth to tenth 
covered with numerous spines; those at the distal extremity of the sixth joint 
are a great deal stouter, and are placed in a complete ring. 

The legs are exactly thrice as long as the body (with the proboscis enclosed) ; 



8 DR P. P. C. HOEK ON THE 

the length of the different joints is as follows : — First and third joint as long as 
the lateral process, at the end of which the leg is inserted. Second joint more 
than thrice as long as the first, slightly swollen towards its distal extremity. 
Fourth joint more than twice as long as the second, and even a little longer than 
the fifth joint. Sixth, seventh, and eighth joints combined once and a half as 
long as the fifth. First to fourth joint almost of the same thickness, fifth to 
eighth joint gradually growing more slender ; all the joints are furnished with 
a longitudiual darker coloured stripe, as is common in Pycnogonids. The first 
three joints of the legs are almost quite smooth, the outer joints rather hairy. 
The structure of the last two joints of the leg can be judged from fig. 5. They 
are not so slender as the same joints of P. longirostris as figured by Wilson. 
The armature, however, is much the same as in that species. 

The only specimen of this species which was collected by the " Triton " is 
a male ; as far as I could make out without mutilating the animal, the small 
genital pores are only present on the two hindermost legs, and situated ventrally 
near the distal extremity of the second joint. The ovigerous leg contains a 
glandular organ with small opening near the beginning of the fourth joint, and 
so does the fourth joint of all the legs. Of the latter the porus is placed at the 
end of a tubular process""" inserted about the middle of the joint. As shown 
in fig. 6, the excretory canal, which passes through the tubular process, has a 
vesicular swelling at its base. Most probably these glandular organs do not 
occur in the females of this species. 

The intestinal caecum which enters the mandible in this species is well 
developed (fig. 2) ; it can be traced till in the last, the claws bearing joint. 
The total length of the body is 8f mm., that of a leg of the hindermost pair 
26 mm. 

Together with Pallene malleolata, Nymphon macronyx, and N. macrum, this 
interesting Pycnogonid was dredged at Station 10 of the cruise of H.M.S. 
" Triton." A young Lamellibranch mollusc (an oyster ?) is affixed to one of its 
legs. 

Mr E. B. Wilson (1881) proposed a new genus for those Pycnogonids 
which come near to Phoxichilidium., M. Edw., but which are characterised by 
three-jointed (four-jointed, Wilson) mandibles and ten -jointed ovigerous legs 
present in both sexes. Moreover, it is distinct on account of the existence of 
rudimentary palpi. Wilson describes two species as belonging to this genus, 
P. forfitifer and P. longirostris, and he supposes that Kroyer's Phoxichilidium 
fiuminense should also be referred to this genus. No doubt he is right in 
this supposition, although the extra articulation of the mandible is wanting 

* Wilson hints that this glandular duct might be a character of generic significance. It occurs, 
however, in numerous genera, as in Phoxichilidium, Oorhynchus, &c. 



PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. "TRITON." 9 

in this species. If the genus Pallenopsis be accepted, four other species of 
deep-sea Pycnogonids, collected during the voyage of H.M.S. "Challenger," 
and described in my report on the Pycnogonids as belonging to Phoxichilidium, 
Milne Edw., belong doubtless to it also. So we have eight species of this 
genus, the range of depth and geographical distribution of which may be judged 
from the following list : — 



Name of the Species. 


Depth in Fathoms. 


Geographical Distribution. 


Pallenopsis flitminensis, Kroyer, spec, 


7-20 


Patagonia, Brazil. 


„ patagonica, Hoek, spec, 


45-175 


Patagonia. 


„ forficifer, Wilson, 


262-333 


Off South Carolina. 


„ longirostris, Wilson, 


500 


South of Cape Cod. 


„ tritonis, n. sp., 


516 


Faroe Channel. 


„ pilosa, Hoek; spec, 


1600-1950 


Southern Indian Ocean. 


„ oscitans, Hoek, spec, 


1675 


Atlantic, West of Azores. 


„ mollissima, Hoek, spec, 


1875 


Off Yeddo (Japan). 



Of these, six are true deep-sea species, the two others are shallow-water 
inhabitants. The deep-sea species have the mandibles three-jointed (as are those 
of the young of Colossendeis and Ascorhynchus) ; the two shallow- water species 
show a transitory form between those with three and those with two-jointed 
mandibles. In the mandible of P. patagonica a trace of an articulation is 
visible dorsally, but totally wanting when seen from the ventral side ; in P. 
fluminensis, a little beyond the middle, the basal joint of the mandibles is 
furnished with a row of hairs, and seems to be divided into two. 

Within the limits of the genus Pattenopsis the change of three-jointed into 
two-jointecl mandibles has taken place. That the three-jointed mandible must 
be considered as the original form is shown by the mandibles of different 
species of Ascorhynchus and Colossendeis ; though they exist in these genera as 
rudimentary or larval organs only and are too small and too weak to be of use to 
the animal, they are distinctly three-jointed. Larval parts, or parts which have 
grown rudimentary, are no more strongly influenced by circumstances ; 
hence they often retain their original condition. No doubt it is a very 
curious coincidence, that the deep-sea species show the original condition of 
the mandibles, whereas the shallow-water forms are furnished with these 
organs in the more robust condition of most of the other genera of Pycnogonids. 

Finally, I wish to point out that the new species for which I have proposed 
the name P. tritonis comes very near to P. longirostris, Wilson. I was long uncer- 
tain whether I should refer my specimen to that species or should describe it as 
a new one. I chose the latter, because of numerous, though perhaps not 
very important, differences between his description and my specimen. Should 

VOL. XXXII. PART I. B 



10 PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. " TRITON." 

the two forms prove identical — as I think it very probable they will do when 
examined comparatively — they give new evidence of the wide range of deep- 
sea species. 



List of the Stations at which Pycnogonids were taken by H.M.S. " Triton." 

Station No. 5, August 9, 1882.— Lat. 60° 11' 45" N., long. 8° 15' W. ; 433 fathoms. Bottom, 

hard ground ; temp. 43°, 5 (Trawl). 
Station No. 6, August 17, 1882.— Lat. 60° 9' N., long. 7° 16' 30" W. ; 466 fathoms. Bottom, 

stones ; temp. 30°-29°, 5 (Dredge). 
Station No. 8, August 22, 1882.— Lat. 60° 18' N, long. 6° 15' W. ; 640 fathoms. Bottom, 

mud; temp. 30° (Trawl). 
Station No. 9, August 23, 1882.— Lat. 60° 5' N. ; long. 6° 21' W. ; 608 fathoms. Bottom, 

mud ; temp. 30° (Trawl). 
Station No. 10, August 24, 1882.— Lat. 59° 40' N, long. 7° 21' W. ; 516 fathoms. Bottom, 

mud ; temp. 46°-49°, 5 (Trawl). 
Station No.^ 11, August 28, 1882.— Lat. 59° 39' 30" N, long. 7° 13' W. ; 555 fathoms. 

Bottom, ooze ; temp. 45°, 5 (Trawl and Dredge). 



EXPLANATION OF PLATE I. 

Figs. 1-6, illustrating Pallenopsis tritonis, n. sp. 

Fig. 1. Animal, dorsal view; magnified 7 diameters. 
Fig. 2. Last joint of the mandible ; magnified 41 diameters. 
Fig. 3. Ovigerous leg ; magnified 7 diameters. 

Fig. 4. Last five joints of the ovigerous leg ; magnified 41 diameters. 
Fig. 5. Last two joints and claw of one of the legs ; magnified 41 diameters. 
Fig. 6. Tubular process of one of the legs ; magnified 94 diameters. 
Fig. 7. Pallene malleolata, G-. O. Sars, dorsal view ; magnified 6 diameters. 
Fig. 8. Colossendeis angusta, G. O, Sars, lateral view of the anterior part of the body ; 
magnified 7 diameters. 

(All the figures are drawn with the camera lucida.) 



jis. Roy. Soc.Edin r 



Vol. mil. Plate I. . 




A.j.WsnaaKth 



PYCNOGONIDA OF THE CRUISE OF H. M. S. TRITON. 



( 11 ) 



II. — Bright Clouds on a Dark Night Sky. By C. Piazzi Smyth, Astronomer- 
Royal for Scotland. (Plates II. to XIV.) 



(Bead 18th June 1883. 



PAQK 
11 



P.AKT I. Statement of the case, and first reference to Meteorological Observations, . . 

Pakt II. Further reference to Meteorology and its computations, . . ... 15 

Part III. Supposed physical cause of the phenomenon. Diagram on p. 18, 17 

Appendix I. Scottish bi-diurnal Meteorological Observations, April 6-10, 1882, ... 22 

Appendix II. Projections of the same in Plates II. to IX., ..... 29 

Appendix III. Continuous hourly observations and their projections in Plates X. to XIV., . 30 

Appendix IV. Further testimony from Royal Observatory, Greenwich ; Gordon Castle ; and Royal 

Observatory, Edinburgh, touching Aurora, . . . . . . . 34 

Part I. 

On a moonless night, whenever clouds of an ordinary elevation in the 
atmosphere appear upon, or pass across, the star-spangled sky behind them, 
they exhibit themselves, as a rule, dark, sometimes even black, in comparison 
therewith. And no wonder, when everypart of the open sky from visible star to 
visible star therein must be lit up to some, though doubtless a very small, extent 
by the faintest general and cumulative radiance of those myriads and myriads 
of lesser stars, which only a large telescope can show to be individually 
existent as actual stellar points of light, but in their aggregate more nearly 
eternal, and still more constant from age to age, than our gigantic Sun itself. 

If the heavens become entirely covered by such clouds, a very dark night is 
the usual and natural result. That at least is my experience on the Calton 
Hill through thirty years of observation ; and something very like it is probably 
so generally recognised as fact over the whole country, that this formal state- 
ment about it, may appear to many persons a needless truism. 

Yet such darkness of elevated midnight clouds is not without exception. 
For on April 8, 1882, on looking out Northward about 9.30 p.m. from an upper 
chamber in the house No. 15 Royal Terrace, to see if there was any Aurora to 
observe, I saw indeed no Aurora, but in place of it two or three decidedly 
luminous clouds, on an otherwise dark by comparison, but star -bearing, sky. 

The rounded forms of these clouds were so contrary to the regular arcs and 
needle-shaped darts of Aurora, and there was so marked an absence of the 
very dark regions which usually appear on the Northern horizon, low down 
underneath an Auroral display, that I went next to the South side of the house, 
and there, to my greater surprise, saw that all the clouds visible from thence 
were luminous with a white, moon-like radiance. Any portions of sky between 

VOL. XXXII. PART I. C 



12 C. TIAZZI SMYTH ON 

them appeared by contrast of pitch-like darkness, though without preventing 
a good sized star from shining forth ; — and the brightness of the clouds con- 
tinually increased from the Zenith down towards the Southern direction, so far 
as the neighbouring Calton Hill allowed one to look into that quarter. 

The affair was so unusual, that I immediately made my preparation for 
going expressly to the top of the said Calton Hill, in order to look further down 
South, and see what strange source of light there could be there, illuminating 
the clouds so strongly ; — for the Almanac declared that there was no Moon in 
the position at that time, nor would be for several hours. 

The ascent of the hill under such circumstances was rather tantalising ; — 
for the first part of the way, by bringing one closer thereto, produces a higher 
angle of obstruction for the summit, — and meanwhile the clouds overhead and 
around, glowed with such an unnatural glare of light, as made me fear it could not 
last long, and that I might be too late after all to see its origin in full force, and 
behold whence it came. Tree tops of neighbouring gardens projected on some 
of these clouds, showed their detail of twigs with almost daylight minuteness'; 
and on coming into view of Nelson's Monument, though still a long way off, 
there was not only the Time-Ball on its summit, but there were its staff and 
cross-arms, each and every one clearly visible and even black and sharp against 
one of these preter-naturally bright clouds. But on reaching the top of the hill, 
and getting a view from thence right down to the Southern horizon, there was 
nothing there in the heavens, or apparently anywhere else to account for the 
strange scene up above. The effect so very strong up there, simply died away 
from inanition in the distance towards the South. 

Baffled then and disappointed I entered the Royal Observatory enclosure 
and watched the strange bright clouds overhead or nearly so, as they were 
wafted about, but chiefly from East to West, for nearly a couple of hours. The 
air was cold and dry. The clouds were of the massive, but irregular figure of 
cumuli when seen at a high angle of altitude, and their light gave to spectro- 
scopic examination nothing but the faintest continuous spectrum in the green 
region. Not in the slightest degree therefore like Aurora, with its sharp citron 
line ; but rather like the faintest trace of carbon-flame illumination. 

Gradually the disastrous and humbling idea grew in my mind,- — that this 
wondrous phenomenon of luminous night clouds was nothing but their reflection 
of the gas-lights of Edinburgh and Leith, Portobello and Granton ; and I tried 
to dismiss the matter from my mind. But every subsequent night that showed 
the usual rule of clouds dark against a starry sky, — though said clouds were 
illuminated by just the same city gas-lights, — brought up the further and per- 
haps more important question " why and how were clouds able to reflect such 
abundant light on that one night of April 8 alone ?" 

Besides the postulate that the air must have been very clear, two other 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 13 

possible reasons suggested themselves. One was, that the clouds were low, and 
therefore nearer the lights that illuminated them. The other, that they affected 
on that night some peculiar physical structure which enabled them to reflect 
with far more than their wonted degree of brilliance. 

The first of these two reasons, however, did not seem very important; for 
though cumulus clouds are never very high in the atmosphere, say about 3000 
feet, rain-clouds are often lower and show no such light ; indeed they are 
usually the blackest of night-clouds. This very circumstance therefore led to 
expecting that the bright appearance of April 8, might be due to just the 
opposite condition of the atmosphere, which moreover did then to some extent 
prevail, in the shape of dry, Scottish spring weather and its undesirable " clouds 
without water." That is without any to fall as rain, though there must have 
been some retained to form the visible mass of the cloud and reflect light with 
extra force. 

Such an idea may bring into play our reason No. 2 ; but before launching 
on that hypothesis, it will be well to ascertain whether there was anything 
extraordinary in the dryness, or indeed in any of the other meteorological con- 
ditions of that one night, contrasting strongly with those of the nights imme- 
diately before and after. 

To this end I have been kindly permitted by the Secretary of the Scottish 
Meteorological Society to make use of the Schedules of that hard-working body. 
And after having selected 24 of them on account of either their topographical 
neighbourhood or high character, I have extracted their bi-diurnal observations 
from April 6 to April 10, or for two days before, as well as two days after, the 
phenomenal night of April 8, as will be seen in Appendix I., and have graphi- 
cally represented their Hygrometry in Appendix II. 

One and one only of the 24 observers says there was Aurora that night ; 
and I have requested the Secretary to communicate with him, and ascertain 
exactly what he saw and how he knew it to be Aurora.* But otherwise there 
was nothing remarkable in any of the returns except the Hygrometric. The 
Barometer was high, about 30*3 inches; the Thermometer low, about 41°0; the 
mean Depression of the Wet-bulb about 2°*5, and the Wind generally from the 
East. 

Now so far as Barometer, Thermometer, and wind are concerned the 
observers were, probably all of them, perfectly competent. But in the more 
delicate and sensitive matter of the Depression of the Wet-bulb by evaporation, 
— I have found it needful to reject three of them for reasons wherein I trust to 
be supported. Thus in a certain case which I will only allude to as No. 14, and 
wherein that usually most varying quantity (Depression of Wet-bulb), is made 
to read exactly 1° degree both morning and evening and day after day through 

* See Appendix IV. 



14 C. PIAZZI SMYTH ON 

almost the whole period, — there was too evidently something, somewhere want- 
ing- in that observer. 

Again in No. 9 the differences from morning to evening are better ex- 
pressed, but the wet-bulb is too often higher than the dry-bulb, to be fully 
credible. And in No. 11, the observer, by simply entering the depression as 
always 1 degree, unless when he sometimes makes it just 2 degrees, shows that 
he is not aware of either the refinement, the truth, or the power of this beau- 
tiful method of arriving scientifically at the Hygrometric state of the air about 
him. 

But of the remaining 21 stations, a notable majority does show a very 
remarkable depression of the wet-bulb to have occurred on the 8th of April, 
1882; and without anything similar to it on the other days, either before or 
after. 

Thus North Esk Reservoir, height 1150 feet, had a wet-bulb depression that 
night of 5° *8, in place of a 3° average. 

Wanlockhead, 1334 feet high, had a depression of 6 0, 8 in place of its 
average 3° - 5. 

Moffat, 350 feet high, had 6°'9, in place of 2°5. 

Greenock, 233 feet high, had 12° 2, in place of 4° -5. 

Paisley, 88 feet high, had 5 o, 0, in place of 3°*5. And 

Glasgow, 54 feet high, had 5° - 0, in place of 2 D, 5. 
While at other stations, the anomaly occurred earlier in the day, or at the 
9 a.m., in place of the 9 p.m. observation : thus — 

Braemar, 1114 feet high, had 4° 5, in place of an average 3 o, 0. 

New Pitsligo, 495 feet high, had 2 0, 6, in place of 1 0, 2. 

Stobo Castle, 600 feet high, had 7°'0, in place of 3 o, 0. 

Stronvar, 428 feet high, had 4 o, 0, in place of 2° J 2. 

Dalkeith, 190 feet high, had 3° -5, in place of 2° 3. 

Callton Mor, 135 feet high, had 13°-0, in place of 4°0. 

Balloch Castle, 93 feet high, had 5°-3, in place of 2° -2. 

Eallabus, 71 feet high, had 8°'0, in place of 4°0. 

Aberdeen, 66 feet high, had 2° '9, in place of 2° 3. And 

Gordon Castle, 104 feet high, had 7°9, in place of 3°8. 
Taken only so far, though very confirmatory on the whole, there are larger 
anomalies among the stations, both as to quantity and time, than is desirable- 
I therefore applied next to Mr W. H. M. Christie, Astronomer-Royal, at 
Greenwich, for the hourly observations of the self-recording dry and wet bulb 
thermometers there ; and made the same request to Mr Robert H. Scott, for 
the returns from the Meteorological Council's Observatories of Glasgow and 
Aberdeen. They kindly responded, and their communicated observations are 
contained in Appendix III. 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 15 

But before using them in the whole, I extracted their 9 a.m. and 9 p.m. 
observations, and projected them in the same manner as had been done with 
the 24 Scottish Stations ; when there came out a most puzzling result ; — viz. 

At Glasgow, in place of the expected evening depression, there was posi- 
tively an elevation. And 

At Aberdeen, in place of the small morning depression of 2 0, 9, there was 
the immense one of 6°*7 ; the average one being only 2°3. 

On using, in place of the single observations of 9 a.m. and 9 p.m., the means 
of the whole 12 hours of observations a.m. and p.m., — the anomalies of the 
curves were largely removed. And at length on projecting every observation, 
and obtaining a nearly continuous history of the wet-bulb depression through 
the whole 24 hours of each of the 5 clays— the anomalies were all most 
abundantly and exquisitely explained. 

An enormous depression, it was thus ascertained, had really occurred at 
Glasgow on the evening of April 8, amounting to no less than 12°"8 ; but it was 
of short duration, and comprised so completely within the interval from 9 a.m. 
to 9 p.m., as not to have affected either of these observations. While at 
Aberdeen, where the Depression had occurred earlier, and to the smaller 
extent of 6°7 only, and lasted less than two hours, — its maximum had just 
struck on the 9 a.m. observation and made that appear excessive. 

The Greenwich observations, very much as might have been expected from 
their great distance, were not sensibly affected by our peculiar Scottish pheno- 
menon of April 8 ; but are extremely instructive for study, and the proof they 
give that 9 a.m. and 9 p.m. observations anywhere, are not sufficient for arriving 
at a knowledge of all the laws of Nature in this department of Meteorology. 

Part II. 

Thus far I have described only the simple results of rude, instantaneous 
observation, viz., the depression of the wet, below the dry, bulb thermometer as 
actually seen by the observer. And though that quantity by itself does not 
give the full or exact Hygrometric state of the atmosphere, it does show forth 
to so large an extent any variations in the same, that I could wish our Scottish 
bi-diurnal observers were instructed to enter that quantity, viz., the depression 
of the wet, below the dry, bulb, as they might so easily do, at the time they 
enter the latter. 

For then, having only one column necessary to look at for instant Hygro- 
metry, they would be far sharper in appreciating changes therein, and the final 
results their observations might lead to, — than when their present two columns 
of mere thermometer figures rather confuse them at the time, and are relegated 
to the Royal Observatory, Edinburgh, at the end of the month, for some one 



16 C. PIAZZI SMYTH ON 

there to find out by computations of another kind, what their instrumental 
readings were equivalent to touching " Humidity ; " but on days then so long 
passed by, as to have ceased to have any vivid interest for the observer. 

To bear on, or illustrate this proposition, all my graphic projections in 
Appendix II. have been arranged so as to give, first, the raw depression of the 
wet, below the drj r , bulb ; and second, the computed Humidity, taking account 
of the Temperature at the time ; and it will be seen that there is no important 
abnormal wave in the latter, that has not its crest, or hollow sufficiently, and 
sometimes more strikingly, marked in the former. The former therefore, which 
every observer can enter for himself at the time with a living interest in it, is 
quite near enough to the scientific truth for all current weather discussions 
whether for agriculturists or gardeners, sailors or country gentlemen. 

But in this particular inquiry of ours on the present occasion, we must do 
something more. Wherefore Mr Heath, 1st Assistant Astronomer in the 
Royal Observatory, has obligingly assisted me by both computing three forms 
of the Hygrometric expression, and also projecting their curves, together with 
that of the Temperature, for all the hourly observations of the three continuously 
working Observatories alluded to. 

Now the projection of the Humidities does not diner much, as already indi- 
cated, from the mere Depressions of the Wet^Bulb. Nor does the projection 
of the Grains-weight of water in a cubic foot of air, except in the way of dull- 
ing and flattening all the curves. But the map of the Grains-weight of water 
still required to saturate each cubic foot, gives an immense result for our par- 
ticular phenomenon of the night of April 8 ; as well as a notable insight into 
some permanent characteristics of climate. 

These permanencies are, that in the North there is very little change 
between clay and night either as to quantity of watery vapour in the air, or the 
further amount required to saturate it. But in the South, teste the Royal 
Observatory, Greenwich, there is an intensity of difference between day and 
night, not in the amount of watery vapour contained in the air, but in the 
further quantity which the air could take up without being saturated thereby, — 
which is not only surprising but warning too ; as it is a condition that lies at 
the root of many of the movements of the atmosphere, and promotes also the 
disruptive, in place of the silent or slow, discharge of atmospheric electricity. 

Looking next to the particular phenomenon of April 8, we find it occurred 
at 9 a.m. at Aberdeen ; and at 4 p.m. at Glasgow ; or crossed the country from 
N. East to S. West at the rate of about 14 miles per hour, increasing in quan- 
tity as it went ; for while it attained to only 0*80 grains at Aberdeen during 2 
hours, it reached 180 grains at Glasgow and lasted there for nearly 8 hours. 
That is, the increased number of grains of watery vapour 'per cubic foot, which 
the air could take up without being saturated. 



BEIGHT CLOUDS ON A DARK NIGHT SKY. 17 

Now as that is the very effect which is experienced in the South every day 
at Noon, as contrasted against Midnight, we might expect that our pheno- 
menon was produced by an elevation of temperature in the air, without time 
given to it to pick up moisture equivalent to its then increased Humidity 
requirements. And this appears to have been the case to some extent, but 
was certainly preceded at Aberdeen on the morning of the 8th, where the 
influence began, by a very unusual decrease of the absolute amount of watery 
vapour contained in the air, — however that decrease was operated. 

Hence in one way or another, dryness of the air was an eminent character- 
istic of the atmosphere though for a limited period, near, or about, or shortly 
preceding the time when the night clouds over Edinburgh appeared luminous 
by excess of brilliancy in their reflection of the city's gas-lights. 

But what does that lead us to, as to the physical manner in which the 
reflection was produced % 



Part III. 

Before entering on this last portion of the inquiry, let me further state, that 
after many and many nights of clouds black on a gently translucent starry sky 
subsequent to April 8, 1882; — there was another most remarkable example of 
clouds bright on a black but still starry sky on Monday April 30, 1883. Those 
unnatural looking bright midnight clouds, as they were wafted hither and 
thither over the heavens by stray currents of air rather than regular winds, had 
almost a fearful splendour, — reminding one of Salvator Rosa's dark Noon-day 
pictures of white clouds overhanging deep rocky gorges among Calabrian 
mountains black as midnight and teeming with treacherous banditti ; and I 
much wondered that honest Edinburgh folk were not out on the streets in 
crowds gazing at, and discussing the strange spectacle. So short-lived too ; 
for the very next night was eminent for the normal blackness of its clouds 
contrasted against the pellucid and star-bearing heavens between them. 

I wrote therefore to the Astronomer-Royal at Greenwich, inquiring whether 
any of the more wide-spreading influences, causes or accompaniments of Aurora, 
were manifested there, on the nights of April 8, 1882, and April 30, 1883, as 
compared with the nights and days immediately before and after these two 
dates. But the reply, as will be seen in Appendix 4, was entirely negative ; 
for neither in Terrestrial Magnetism, Earth currents, atmospheric electricity, or 
Sun-spots was there anything noteworthy going on at either of those times. 

Relieved therefore of any Cosmical phenomenon to attend to, — let us now 
look at the matter in its more ordinary terrestrial character. 

On June 25, 1882, at the rather elevated station of Buxton, in high Derby- 



18 C. PIAZZI SMYTH ON 

shire, I witnessed a remarkable proof that " cumulus " clouds can assume, and 
keep up for a short time, an excessive brilliancy of reflection. 

The case was this ; at 6 p.m. when walking in the Park there, and looking 
S. East, I noted and sketched the half-Moon and a great thunder-cumulus' 5 ' 
cloud close to it thus, 




The Moon was exceedingly pale as compared with the great mass of the 
cloud on which the Sun was shining out of a clear sky in the West. The 
cloud was indeed estimated at 7 to 10 times as bright as the Moon ! This 
extreme brightness of the cloud however only lasted about half an hour; when 
its brighter part went down to something like 3 times that of the Moon. 

But as Sir John Herschel well remarked in his " Cape Observations," and 
when contrasting tclescopically the brightness of the Moon setting behind the 
summit-cliff of Table Mountain, with that cliff then illuminated by the brilliant 
rising Sun of South Africa, — their then brightnesses were equal, just as their 
illuminations by the Sun, at the same distance therefrom in space, were equal 
also. But the solid surface of the Moon must be a nearly constant of reflect- 
ing power ; therefore when it was so vastly transcended in brightness by the 
Buxton cloud in daylight, — the said cloud must have been an anomaly surpass- 
ing all ordinary terrestrial surface materials in reflective power, just as did the 
Edinburgh night clouds when distinctly luminous from their reflection of gas- 
lights far below them. 

What enabled clouds then, on these two or three occasions, to reflect so 
very strongly whatever light, whether Solar, or artificial, that struck upon 
them ? The only reason I can suggest powerful enough for the occasion, but 
one that seems to fulfil all the conditions, is, — that the molecules of the clouds 
were then in a hollow, vesicular condition, rather than drops or spherules of 
water. The former state is evidently most compatible with their floating in 

* The thunder-cumulus, when weather is approaching a condition for electric discharge differs 
from the ordinary cumulus cloud, by being more tightly made up as it were, and with smaller or sort 
of cauliflower figures. 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 19 

the air for any length of time and dropping no water ; whereas the latter is the 
very preparation for rain-fall. This latter too is the condition of least reflection 
and most absorption of light, while the former is that of least absorption and 
most reflection. 

These propositions may be practically established most easily by earth- sur- 
face examples, where the nature of the molecules may be most easily examined. 
Falling rain drops, even when directly shone on by the Sun and forming a rain- 
bow, are anything but bright, unless indeed they are mixed with hail. And if 
we take water in the largest shape, what is there so dark as the deep blue sea, 
whence comes to our eyes only a faint, "first surface " reflection, from a sphere 
of stupendous size ; and yet what is so brightly white as the foam of the same 
material when arranged in numerous, small coalescing convex vesicles, eveiy 
one of them reflecting from both the first, and more especially the second, 
surface of its film, whatever point or gleam of light there may be in the whole 
hemisphere illuminating them. 

Or again how dark brown is the water of a peaty hill in the Highlands when 
in a placid state, reflecting by means of only its first surface ; and yet how 
brightly white is the course of a stream of it viewed from a distance on the 
mountain side and even under a cloudy sky, when it has to chafe and 
tumble down rocky channels, wherein it covers itself with foam, or in- 
numerable little hemispherical bubbles on bubbles, each of which gives us, 
both the weak first, and the strong second, reflection of a film of water, or glass 
plate in air. 

That is, such a frothy surface is bright when we look upon it from above, 
or the side whence, by day, comes its chief, or only illuminating light ; as snow 
also then appears most intensely white. But when we look at either snow, 
or froth of water between us and the chief light, they appear dark rather 
than bright ; for they reflect far too well, to allow much to be transmitted 
through them. 

But still more particularly what can be brighter than those fields of apparent 
snow, the upper surfaces of the clouds composing the great cloud stratum of 
the low N. East, or commencing Trade, wind, as seen day after day in the 
summer season from the summit of the Peak of Teneriffe, at a depth of several 
thousand feet below : and they are known to be in the watery, as contra-dis- 
tinguished to the frozen, condition. And yet what is darker and more threaten- 
ing than the appearance of the same clouds, when seen from below, or between 
the observer and the Sun-illumined hemisphere of sky. 

There too, at or near the sea level, in a moist air, rain does sometimes fall 
from those clouds' lower dark surfaces, where their component molecules may 
be increased in size with acquired outside moisture until they become practi- 
cally drops of water. But above, on their upper surfaces, where to an observer 

VOL. XXXII. PART I. D 



20 C. PIAZZI SMYTH ON 

higher still, they appear so blindingly white, they come into contact with "the 
Tenerifte air above the clouds " (i.e., the clouds of the lower N. East wind), 
which air is dry to the last degree ; dry even to a depression of from 25 to 30 
degrees Fahr. of the wet, below the dry, bulb Thermometer. Now this is a 
state of things which must evaporate the outside of the watery cloud-molecule; 
and if there be, as I believe has long since been generally held, a hollow or air 
centre to it, must leave the watery coating portion only as a thin shell sur- 
rounding such air particle. In which case such shell will reflect from a second 
surface almost as large as the first, and with a very minimum of absorption by 
fluid material. 

Such thinning indeed of the vesicle, as pointed out lately by Professor Alex. 
Herschel, must not be carried too far ; or, like the black centre of Newton's 
rings, there will supervene an incapacity to reflect any light ; immediately after 
which, the vesicle must burst, and cease to be a visible existency. As this 
termination of the life of cloud molecules — which are seen by travellers who 
ascend the peak, to be continually rising into the upper air, but never getting 
beyond a certain level therein,* — must take place more rapidly the drier the 
medium, it results that the whole cloud seen in the distance will have a harder, 
better defined ontline, on the side where the air is dry, than that where it is 
moist; or according to Nature's general law, above, rather than below, the level 
of the N. East wind's clouds. 

Now the night clouds of April 8, 1882, which belonged to such N. East 
weather, showed well-compacted, almost case-hardened surfaces below, or when 
looked at from below, which was also at that time, the direction from which 
their chief illumination came, viz., the city gas-lights. And if their lower 
surfaces were then so compact, and could then reflect so powerfully, as they 
undoubtedly did that night, it must have been because there was at that time 
a stratum of air below them, as remarkably dry as the classic stratum which is 

* This feature is well set forth by Dr Marcet, F.K.S., in his recent hook Southern and Swiss 
Health Resorts, p. 262 ; except that he speaks of the return S. West current as being immediately 
above the cloud, in place of, as it is throughout all the summer season, separated from it by a thickness 
of full 5000 feet of a gradually decreasing strength of N. East wind, the same in direction as what prevails 
both below, and in, the cloud level, but differing hygrometrically therefrom exceedingly, in being extra- 
ordinarily dry. This important physical peculiarity is afterwards, however, fully acknowledged by Dv 
Mabobt at pp. 296 to 306 of his useful book. For he there sets forth in a fuller and more serious 
manner that the N. East cloud level is never so low as 1200 feet, but nearer to 3000 feet high; and 
by its shade moderates both the temperature, the radiation and the moisture of the country below it. 
l!ut at his Guajara station, 7090 feet high and therefore altogether above that N. East cloud level, he 
found there was still a prevailing tendency of the wind to blow from the North East, but accompanied 
by a terrific dryness, amounting on one occasion to 30° - 5 depression of the wet, below the dry, bulb 
thermometer. Even on the higher central Peak, at 10,700 feet elevation, he says that " the -S. West 
current, bringing hack moisture from between the tropics," was only beginning to be felt ; and the 
traveller would have to ascend several thousand feet higher still, if he could, to reach the full force and 
volume of that important stratum, at that season. All which exactly agrees with my own experience, 
described in Tenenffe, an Astronomer's Experiment, in 1856. 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 21 

otherwise always above, any massive cumulus clouds, as testified by the 
Teneriffe observations of 27 years ago. 

But the whole purport of the Meteorological data we have collected and 
discussed from 27 Observatories, large and small, shows without contro- 
versy that a most unusual wave of dryness did pass across Scotland on that 
particular 8th of April day. Below the level of the clouds too, because so 
distinctly perceived and felt on the inhabited surface of the earth ; but having 
its maximum probably at 2000 feet or more above the sea-level, because 
recorded as greater in amount at the hill, than the valley (but everywhere beneath 
the clouds), stations of the Scottish Meteorological Society. 



22 



C. PIAZZI SMYTH ON 



APPENDIX I. 

Bi-Diurnal Observations from April 6-10, 1882, at 24 Stations of the Scottish Meteorological 

Society, and 3 Government Observatories, 



Station. 


Date. 


A, ^ 

o -3 

fa s 


Hygrometer 

,'lt 9 A.M. 

and 9 p.m. 


Hysrometrical 
Computed Results. 


Wind 
at 5 a.m. 
and 9 p.m. 


Clouds. 


c 

D 




o 

O 





Remarks. 


00 

5. 

■< 


■a 

m 


S 
H 


o . 

= 3 

Q 


1 ^ 


t cu o 

Z ?* o 

a O 
> rH 


— o 


c" 

o 

5 


. O 

T. O 

s £ 

o 3 

CD JU 
O 


a 

a 

"5 

s 


o 
o 

a 

o 
E 
< 


Edinburgh, 
No. 1. 

162 feet. 

Lat. 55° 57' N. 
Long. 3 3 11' W. 




ins. 
30-54 
30-60 
30-67 
30-71 


427 
41-1 
43-2 
39-0 


41°-8 
38-7 
40-8 
38-7 


0°9 
2-4 
2-4 
0-3 


grs. 
3-0 
2-4 
2-6 

2-7 


gr- 
0-2 
0-6 
0-6 
0-1 


93 

81 
81 
98 


E. 

e. 

E. 
E. 


2-6 
2-2 
2-6 
2-9 




6-8 
2-3 


hrs. 
6-0 

9-3 


2 
"i 


o-o 
o-b 




•{ 


30-68 
30-67 


43-2 
39-2 


40-8 
38-3 


2-4 

0-9 


2-6 

2-6 


0-6 
0-2 


81 
93 


E. 

N.E. 


2-2 
2-6 




0-5 


10-8 





o-o 






30-52 
30-37 

30-25 
30-17 


38-7 
36-7 

38-4 
36-9 


36-7 
35-7 

37-7 
34-7 


2-0 
1-0 

0-7 
2-2 


2-3 
2-3 

2-6 
2-0 


0-5 
0-2 

0-2 
0-5 


84 
92 

94 
82 


S.E. 
S.E. 

E. 
E. 


1-7 

2-0 

2-2 
20 




3-5 
3-5 


6-5 
6-5 


4 



o-o 
o-o 


(5 p.m. Fine dis- 
< play of cirri cloud 

( over whole sky. 


Means, . 




30-52 


39-9 


38-4 


1-5 


2-5 


0-4 


88 




2-3 












Braemar, 
No. 2. 

1114 feet. 

Lat. 57 N. 
Long. 3° 24' W. 




30-52 
30-57 
30-59 
30-64 


39-7 
35-0 
30-0 
36-9 


37-9 
34-3 
28-8 
33-5 


1-8 
0-7 
1-2 
3-4 


2-4 
2-2 
1-6 
1-8 


0-5 
0-2 

0-4 
0-8 


86 
93 
80 
73 


N.E. 
N.E. 

E. 

E. 


1-0 
0-2 







8 
Fog. 








> Clear and fair. 
Do. 


M 


30-60 
30-54 


36-7 
37-7 


32-1 
35-2 


4-6 
2-5 


1-6 

2-1 


0-9 
0-6 


63 

80 


E. 
E 
















> Clear and fair. 


10 j 


30-41 
30-31 
3016 
30-14 


37-7 
39-4 
42-2 
34-4 


32-5 
36-7 

37-7 
32-8 


5-2 
2-7 
4-5 
1-6 


1-6 
2-2 
2-1 
2-0 


1-1 

0-6 
1-0 
0-4 


61 

79 
69 

84 


E. 

E. 

S.E. 

E. 





0-2 





1 








> Clear and fair. 
1 Do. 


Means, . 




30-45 


37-0 


34-2 


2-8 


2-0 


0-7 


77 




o-i 












North Esk 
BBTOIB, 

3. 

1150 feet. 

Lat. 55° 48' N. 
Long. 3° 21' W. 


•1 


30-47 
30-68 

30-60 

:;u-i;:i 


40-5 
87-5 

40-5 
32-5 


39-5 
36-5 
38-1 
31-5 


1-0 
1-0 
2-4 
1-0 


2-7 
2-4 
2-4 
1-9 


0-2 
0-2 
0-6 
0-2 


92 
91 
81 

88 


N.E. 

E. 
S.E. 

E. 


4-0 
4-0 
4-0 
4-0 




Mist. 
Nimb. 






3 

10 








•< 


30-61 
80-54 


42-5 


36-8 
29-5 


5-7 
4-0 


1-9 
1-4 


1-2 

0-8 


62 
61 


E. 
10. 


4-0 
4-0 








12 






) Hoar frost. 
) Clear line day. 


•{ 


30-43 
30-29 
30-18 
30-10 


32-1 
31-5 


31-5 
29-5 
43-5 
38-6 


0-6 
2-0 
4-0 
20 


2-0 
1-6 

2-8 
2-0 


0-1 
0-6 
1-0 
0-4 


92 

71 
74 
82 


S.E. 

N. 

N. 
Var. 


4-0 
1-0 

1-0 
4-0 




Fog. 


5 


7 
12 






Fog. 
Cirro-stratus, fine. 


.Means, . 




30-44 


37-4 


35-0 


2-4 


2-1 


0-5 


80 




3-4 













BRIGHT CLOUDS ON A DARK NIGHT SKY. 



23 



Station. 


Date. 


03 m 
CO c 
O * 

« a 
8 •« 

■§2 

?°° 
B» 

3 3 
pq a 


Hydrometer 
at 9 a.m. 
and 9 p.m. 


Hygrometrical 
Computed Results. 


Wind 
at 9 A M. 
and 9 p.m. 


Clauds. 




c 
3 

CO 


a 






*c5 


Remarks. 


00 
00 

< 


*3 
"3 

ca 

is 


a 

CI 

s 


o 


g — 

§• c 

> o 

1 2 


^ D O 

111 

•- S a 
3 3 
c •% 

a V 

> rH 


-£0 

™ 

!i 


a 



s 


. O 

c £ 

» in 

c 


5 






3 
< 


Wanlockhead, 
No. 4. 

1334 feet. 

Lat. 55° 24' N. 
Long. 3° 48' W. 




ins. 
30-39 
30-48 
30-55 
30-58 


41° 1 
39-0 
42-9 
37-0 


40°1 
36-4 
38-5 
36-5 


1°0 

2-6 

4-4 
0-5 


grs. 
2-7 
2-2 
2-2 
2-4 


gr. 
0-3 
0-6 

1-0 
0-2 


92 

80 
70 
96 


E. 
E. 
E. 
E. 


4-0 
1-0 
4-0 
0-2 


E. 
E. 


10 
2 




hrs. 

12 

12 








»{ 


30-57 
30-47 


40-3 
40-5 


36-0 
33-7 


4-3 
6-8 


2-0 
1-5 


1-0 
1-4 


68 
53 


W. 
S.W. 


0-2 
0-2 








12 








9 { 
10 j 


30-40 
30-29 
30-17 
30-08 


30-2 
36-3 
42-8 
36-1 


29-9 
35-2 
40-0 
36-0 


0-3 
1-1 
2-8 

o-i 


1-9 
2-2 
2-5 
2-5 


0-1 
0-3 

0-7 
0-0 


95 
90 
79 
99 


W. 

W. 

W. 

NAY. 


0-2 
0-2 




W. 



1 
1 
6 


13 
6 








Means, . 




30-40 


38-6 


36-2 


2-4 


2-2 


6 


82 




1-0 












Marchmont 

(Berwick), 

No. 5. 

500 feet. 

Lat. 55° 44' N. 
Long. 2" 25' W. 




30-49 
30-57 
30-66 
30-66 


43- 
43- 

41- 
38- 


39- 
42- 
39- 
37- 


4- 
1- 
2- 
1- 


2-3 
2-9 
2-5 
2-4 


0-9 
0-3 
0-5 
0-3 


71 
92 
84 
91 


E. 
E. 
E. 
E. 


9-0 
9-0 
1-0 
4-0 


E. 
E. 
E. 


10 
8 
8 



3 
6 








8 { 


30-67 
30-59 


41- 
39- 


39- 

38- 


2- 
1- 


2-5 
2-5 


0-5 
0-3 


84 
92 


E. 
E. 


1-0 

4-0 


EJ 



10 


8 








:o| 


30-50 
30-34 
30-24 
30-14 


39- 
34- 
35- 
36- 


36- 
34- 
34- 
35- 


3- 

o- 

1- 
1- 


2-1 
2-3 
2-1 
2-2 


0-7 
0-0 
0-3 
0-3 


77 

100 

90 

91 


E. 
E. 

N.E. 
N.E. 


1-0 

4-0 
4-0 
4-0 


E. 

E. 

N.E. 
N.E. 


10 

5 

10 

10 


8 
4 








Means, . 




30-49 


38-9 


37-3 


1-6 


2-4 


0-4 


87 




4-1 








. .. 






Dalkeith, 
No. 6. 

190 feet. 

Lat. 55° 54' N. 
Long. 3° 4' W. 




30-54 
30-60 
30-68 
30-68 


45-7 
43-0 
45-3 
39-5 


41-3 
40-5 
41-5 
38-5 


4-4 
2-5 
3-8 
1-0 


2-5 
2-6 

2-6 
2-6 


1-0 
0-6 
0-9 
0-2 


70 
81 
74 
92 


N.E. 
N.E. 

N.E. 
N.E. 


- 








(2 





M 


30-69 
30-61 


45-5 
37-0 


42-0 
35-5 


3-5 

1-5 


2-6 
2-2 


0-8 
0-4 


75 
87 


N.E. 

N. 
















30-52 
30-36 
30-26 
30-18 


39-5 
36-0 
38-5 
37-3 


37-5 
35-5 
37-7 
35-5 


2-0 
0-5 
0-8 
1-8 


2-3 
2-4 
2-6 
2-2 


0-5 
0-1 
0-2 
0-5 


84 
96 
94 
85 


E.N.E. 

E.S.E. 

W. 














Means, . 




30-51 


40-7 


38-6 


2-2 


2-5 


0-5 


84 










r 

r 






Smeaton, 
No. 7. 

100 feet. 

Lat. 56° 3' N. 
Long. 2° 40' W. 




30-50 
30-61 
30-67 
30-68 


44-5 
42-3 
44-5 
38-0 


43-2 

40-2 
42-2 
37-0 


1-3 
2-1 
2-3 
1-0 


3-0 
2-6 
2-8 

2-4 


0-3 
8-5 
0-6 
0-3 


90 
84 
83 
91 


E. 
E. 
E. 
E. 






8 
8 
3 
3 


7 
6 
6 
5 


o-io 




»{ 


30-70 
30-63 


44-5 
37-5 


42-7 
36-2 


1-8 
1-3 


2-9 
2-3 


0-5 
0-3 


87 
89 


E. 
E. 






2 
3 


8 


4 
3 








30-51 
30-39 
30-27 
30-19 


40-5 
36-5 
39-0 
33-5 


38-2 
35-2 
38-2 
32-8 


2-3 
1-3 
0-8 

0-7 


2-4 
2-2 
2-6 

2-1 


0-6 
0-3 
0-2 

o-i 


82 
89 
94 
92 


E. 
E. 
E. 

E. 






8 
1 
6 
2 


8 
5 


4 
6 
4 
5 






Means, . 




30-52 


40-1 


38-6 


1-5 


2-5 


0-4 


88 

















24 



C. PIAZZI SMYTH ON 





Station. 


Date. 


« C 

aj 

- < 
s 9a 

S^ 

<U CD 
CT3 

= I 

a 


Hygrometer 

lit 9 A.M. 

and 9 P.M. 


Hj-grometrical 

Computed Uesulls. 


Wind 
at 9 a.m. 
aud 9 p.m. 


Clouds. 


a 
3 

c 
a 


a 

o 

o 


d 


Rejlauks. 




OO 

00 

a 


J3 

3 
a 

a 


3 

CO 


a 
ad 

.2 3 
ij« 

a 


3 < 

"3 (5 


■a < 
wo 

> H 


.- o 

1". 

tCco 


a 
o 

u 

a 


en 

a 

o 


c 

o 

5 


O 
1 

o 

1" 

o 

s 




East LrxTON, 
No. 8. 

90 feet. 

Lai 55° 59' N. 
Long. 2' 16' W. 




ins. 
30-53 
30-57 
30-67 

30-67 


43°0 
44-8 
46-0 
39-0 


40°-5 
393 
43-0 
37-0 


2°5 
5-5 
3-0 

2-0 


grs. 
2-6 
2-2 

2-8 
2-3 


0-6 
1-3 

0-8 
0-5 


81 
63 

79 
84 


E. 
E. 
E. 
E. 


0-2 
0-2 
0-2 
0-2 


E. 
E 


4 

10 

2 


hrs. 
10 

12 


6 
4 
4 
6 


o-io 






»{ 


30-67 
30-62 


46-2 
38-0 


43-5 
360 


2-7 

2-0 


2-9 

2-2 


0-7 

0-5 


82 
83 


E. 
E. 


0-2 
0-2 


e! 


2 
8 


10 


5 
4 








•i 


30-51 
30-35 
30-25 
30-15 


41-0 
36-3 
40-0 
35-5 


37-9 
33-5 
38-0 
32-8 


3-1 

2-8 
2-0 

2-7 


2-3 
1-9 
2-4 
1*8 


0-7 
0-7 
0-5 
0-6 


76 
76 

84 
76 


N.B. 
E. 
E. 
W. 


0-2 

o-o 

0-2 

o-o 




7 
1 
2 
2 



10 


8 
3 
3 
6 








}] tans, . 


, 


30-50 


41-0 


38-2 


2-8 


2-3 


0-7 


7S 




0-2 












•a ( 

o 
a 


Haddington, 
No. 9. 

240 feet. 

Lot. 55° 57' N. 
Long. 2° 47' W, 


•J 


30-52 
30-61 
30-66 
30-67 


44-2 
41-2 
46-0 
38-5 


43-7 
40-5 
44-5 
39-0 


0-5 
0-7 
1-5 

?(+0-5) 


3-2 
2-8 
3-2 


o-i 

0-2 

0-4 


96 
95 

89 


S.E. 
E. 
E. 
E. 


1-0 
1-0 
1-0 
1-0 




8* 

9- 
4- 

o- 






o'-oi 






■4 


30-68 
30-58 


45-2 
36-2 


44-0 
37-0 


1-2 

1 (+0-8) 


3-1 


0-4 


91 


E.N.E. 
E. 


1-0 
1-0 




3- 

o- 










2 « 
on J? 


•< 


30-49 
30-35 
30-21 
30-16 


48-5 
36-5 
43-2 
36-0 


48-2 
36-5 
44-2 
35-2 


0-3 

o-o 

?(+l-0) 
0-8 


3-8 
2-5 

2*3 


0-1 

o-o 

0-2 


98 

100 

93 


E.N.E 

N.E. 

E. 

E. 


1-0 
1-0 
1-0 
10 




6- 
0- 

7- 
0- 










DO 
2 


Means, . 




30-49 


41-6 


41-3 


0-3 










1-0 
















Stobo Castle, 
No. 10. 

600 feet. 

Lit. 55' 35' N. 
Long. 3" 25' W. 




30-47 
30-57 
30-61 
30-65 


42-0 
4O-0 
42-0 
38-0 


41-0 
38-0 
40-0 
36-0 


1-0 
2-0 
2-0 
2-0 


2-8 
2-4 
2-6 

2-2 


0-3 
0-5 
0-5 
0-5 


92 
84 
85 
83 


E. 
E. 
E. 
E. 












a 

1 
o 






M 


30-63 
30-55 


40-0 
36-0 


33 
35-0 


7-0 
1-0 


1-5 
2-2 


1-4 

0-3 


51 
91 


N.W 
E. 


















30-49 

311-33 

30-20 
30-13 


30 -0 
34 
40-0 
390 


33-0 
33-0 
32-0 
37-0 


3-0 
1-0 
8-0 

2-0 


1-8 
f 1 
1-4 
2-3 


0-7 
0-2 
1-5 

0-5 


74 
89 
46 

84 


E. 
E. 
S. 
E. 














o 

o 
9 

It 
£'3 

ft- 


Means, . 




30-46 


38-7 


35-8 


2-9 


2-1 


0-6 


78 
















Cdfab (Fife), 
No. 11. 

210 feet. 

Lat. 68" 10' X. 
Long. 3° 6 W. 


•< 


30-54 
30-52 
30-69 

3u-i;;i 


44- 
45- 
44- 
45- 


43- 
44- 
43- 
43- 


1-0 
1-0 
1-0 
2-0 


3-0 
31 
3-0 
2-9 


0-3 
0-3 
0-3 
0-5 


92 
92 
92 

85 


E. 
E. 
E. 
E. 


4-0 
1-0 
1-0 
1-0 








— — 


d 

M 

o 
ft 


. 


1« 


■J 


30-71 
30-63 


45- 
46- 


44- 
44- 


1-0 
2-0 


3-1 
3-1 


0-3 
0-5 


92 

86 


B. 

10. 


1-0 
1-0 








.■a 

I 1 

«5 




30-49 
80-38 

30-26 
3017 


37- 
38- 
38- 
39- 


36- 
37- 
36- 
38- 


10 
1-0 
2-0 
1-0 


2-3 
2-4 

■2-2 
2-5 


0-3 
0-3 
0-5 
0-3 


91 
91 
83 
92 


E. 
E. 
E. 
E. 


1-0 
1-0 
1-0 
1-0 












1 


Means, . 




80-6] 


42-1 


40-8 


1-3 


2-8 


0-4 


90 




1-3 


















BRIGHT CLOUDS ON A DARK NIGHT SKY. 



25 



Station. 


Date. 


> . 

o 9. 

e3 ^ 
00. g 

o ^ 
re S 

o *^ 

a OS 

If 

p rz 


Hygrometer 
at 9 a.m. 
and 9 p.m. 


Hygrometrical 
Computed Resulte. 


Wind 
at 9 a.h. 
and 9 p.m. 


Clouds. 


a 

a 
a 

09 


e 

o 
O 


a 
'3 

PS 


Remarks. 


QO 
QD 

S 


■2 
B 


pq 
e 


o 
c ^ 

Pte 

p 


a < 
o ^ 

°*" ° 
> 5 

■S.S£ 

-w o 
CO •§ 

% iH 


a = ° 


™ o 

|ll 
"so 


a 

o 

o 

s 


v O 

c 
o 


a 
o 

5 


o* 

o 

a 
o 

s 
< 


Glasgow, 
No. 12. 

54 feet. 

Lat. 55° 53'N. 
Long. 4° 18' W. 




ins. 
30-50 
30-57 
30-64 
30-67 


45°0 
42-5 
44-5 
40-5 


43°-0 
39-5 
41-0 
38-0 


2°-0 
3-0 
3-5 
2-5 


grs. 
2-9 
2-4 
2-6 
2-4 


gr. 
0-5 
0-7 
0-8 
0-6 


85 
78 
74 
80 


E.S.E 
E.S.E. 

E. 
S.E. 


9-0 
4-0 
4-0 
1-0 






hrs. 




"5 
o 




»{ 


30-67 
30-60 


44-0 
41-5 


41-0 
36-5 


3-0 

5-0 


2-6 
2-0 


0-7 
1-1 


77 
65 


E. 
E. 


4-0 
1-0 














30-51 
30-34 
30-23 
30-14 


39-5 
41-5 
34-0 
39-5 


37-0 
45-0 
34-0 
37-5 


2-5 
1-5 

o-o 

2-0 


2-2 
2-6 
2-3 

2-4 


0-6 
0-4 
00 
0-5 


80 

89 

100 

84 


E.S.E. 
E.S.E. 
S.S.E. 
E.S.E. 


1-0 

1-0 
0-2 
0-2 












Means, . 




30-49 


41-2 


38-7 


2-5 


2-4 


0-6 


81 




2-5 












Balloch Castle, 
No. 13. 

93 feet. 

Lat. 56" 1' N. 
Long. 4° 35' W. 




30-53 
30-63 
30-67 
30-71 


45-5 

41-7 
44-5 
40-5 


44-1 
39-1 
41-6 
38-6 


1-4 

2-6 
2-9 
1-9 


3-1 
2-4 

2-7 
2-5 


0-4 
0-6 
0-7 
0-5 


89 
81 

78 
85 


N.E. 

N.E. 

N.E. 

E. 


9-0 
9-0 
4-0 
4 






8 
11 








>{ 


30-70 
30-63 


46-0 
41-0 


40-6 
38-6 


5-4 

2-4 


2-3 

2-4 


1-3 

0-6 


67 
81 


N.E. 
E. 


4-0 

0-0 






12 










30-54 
30-39 
30-27 
30-18 


37-0 
47-5 
37-0 
41-5 


35-8 
45-6 
36-6 
39-8 


1-2 
1-9 
0-4 
17 


2-3 
3-2 
2-5 

2-6 


0-3 
0-5 

o-i 

0-4 


89 

87 
96 

87 


E. 

S.E. 
S.E. 
S.E. 


o-o 

o-o 
o-o 
o-o 






10 

7 








Means, . 




30-52 


42-2 


40-0 


2-2 


2-6 


0-5 


84 




3-0 














Castle-Douolas, 
No. 14. 

783 feet. 

Lat. 55° 35' N. 
Long. 3° 52' W. 


•{ 


30-48 
30-55 
30-61 
30-65 


42-1 
37-1 
36-1 
35-1 


41-6 
36-1 
35-1 
34-1 


0-5 
1-0 
1-0 
1-0 


3-0- 
2-3 
2-2 
2-1 


o-i 

0-3 
0-3 
0-3 


96 
91 
91 
90 


E. 
N.E. 
















»{ 


30-64 
30-56 


38-1 
35-1 


37-1 
34-1 


1-0 
1-0 


2-4 
2-1 


0-3 

0-3 


91 
90 


N. 












... 






30-45 
30-35 
30-24 
30-14 


31-6 
37-1 
33-1 

34-1 


30-1 
36-1 
32-1 
33-1 


1-5 

1-0 
1-0 
1-0 


1-6 
2-3 

2-0 
2-1 


0-5 
0-3 
0-2 
0-2 


81 

91 
89 
89 


N.E. 

s." 










E 


... 




Means, . 




30-47 


36-0 


35-0 


1-0 


2-2 


0-3 


90 


















Moffat, 
No. 15. 

350 feet. 

Lat. 55° 21' N. 
Long. 3° 27' W. 


«{ 
'{ 


30 : 54 
30-62 
30-63 


45-8 
42-0 
46-8 
43-0 


43-0 

39-0 
46-2 
42-8 


2-8 
3-0 
0-6 
0-2 


2-8 
2-4 
3-5 
3-1 


0-7 
0-7 
0-2 
0-1 


80 
78 
96 
98 




- 














M 


30-61 
30-54 


53 
42-8 


53-0 
36-0 


o-o 

6-8 


4-5 

1-7 


o-o 

1-5 


100 
56 










— — 








»{ 
Mj 


30-48 
30-35 
30-22 
30-11 


43-5 
40-0 
45-0 
40-5 


38-0 
38-0 
42-8 
30-5 


5-5 

2-0 

2-2 

10-0 


2-0 
2-4 
2-9 
1-1 


1-2 
0-5 

0-5 
1-8 


62 
84 
84 
38 














j Hard frost at 
t night. 


Means, . 




30-46 


44-2 


40-9 


3-3 


2-6 


07 


78 



















3£ 

oa>-i 

3d 
a) to 

°2 



26 



C. PIAZZI SMYTH ON 



Station. 


Date. 


1 a 

1 -3 

DO S 
O « 

S a 

3m 

2 rt 

O CO 

a* 

£ i 
e 3 


Hj | rometer 
al 9 a.m. 
ninl 9 p.m. 


Hygrometrlcal 
Computed Results. 


Wind 
and 1) P.M. 


Clouds 


I 


3 
o 

O 


M 


Remarks. 


< 


a 

G 


d 

3 

pq 


o . 

= 5 

C 3 

f« 

§•£ 

Q 


C 

„_ 

§• = 
> 1 

1 1 


■a 5 

■a s *= 

S-2 § 

'i- = fe 

~ rt o 

IS1 

> r* 


.- o 

T3 rt 
3 II 


3 
O 

s 


. 3 

s £ 

9 3 
god 

^ .3 

- — ' 
o 


E3 

o 

3 


o 

1 
o 

3 
3 
o 

s 
< 


Stbonyab, 

No. 16. 

428 feet. 

Lat. 56° 20' N. 
Loug. 4° 20 \Y. 


*{ 


ins. 
30-52 
30-59 
30-66 
30-64 


44- 
39- 
42- 
37- 


41- 
36- 
39- 
35- 


3° 
3- 
3- 
2- 

4- 

2- 


grs. 
2-6 
2-1 
2-4 
2-1 


gr- 
0-7 
07 
07 
0-5 


77 
77 
78 
83 


E. 
E." 


4-0 
0-2 






Ills. 








>{ 


30-66 
30-57 


42- 
36- 


38- 
34- 


2-2 
2-0 


0-9 
0-5 


72 
82 


E. 


1-0 














10 { 


30-49 
30-33 
30-23 
30-13 


32- 
34- 
36- 
42- 


31- 
33- 
35- 
39- 


1- 
1- 
1- 
3- 


1-9 

2-1 
2-2 

2-4 


0-2 
0-2 
0-3 

0-7 


87 
89 
91 

78 


E. 
N.E. 


0-2 

1-0 














Means, . 


■ 


30-48 


38-4 


36-1 


2-3 


2-2 


0-5 


81 


















Greenock, 

No. 17. 

233 feet. 

Lat. 55° 57' N. 
Long. 4° 45' W. 




30-51 
30-54 
30-64 
30-61 


44-2 
47-2 
42-2 
53-2 


42-2 
42-7 
38-7 
46-7 


2-0 
4-5 
3-5 
6-5 


2-8 
2-6 
2-3 
2-8 


0-5 
11 
0-8 

1-7 


84 
70 
75 
62 


E. 
E. 

E. 
E. 


2-2 
1-0 

2-2 
0-2 




10 

5 











>{ 


30-66 
30-57 


43-2 
55-2 


37-9 
42-9 


5-3 
12-3 


2-1 
1-9 


1-2 
3-1 


63 

40 


E. 
E. 


2-2 
1-0 




5 












•{ 


30-52 
30-35 
30-22 
30-14 


36-0 

49-0 
37-2 
48-2 


33-9 
44-9 
36-7 
43-7 


2-1 
4-1 
0-5 
4-5 


2-0 
2-9 
2-5 

2-7 


0-5 
1-1 
0-1 
1-1 


81 
72 
96 
70 


E. 
W. 
E. 
E. 


0-2 
1-0 
1-0 
0-2 




10 



Nimb. 

5 










Means, . 




30-48 


45-6 


41-0 


4-5 


2-5 


1-1 


71 




1-1 














Paisley, 
No. 18. 

88 feet. 

Lat. 55° 5C N. 
Loug. 4° 27 W. 


•1 
'1 


30-49 
30-56 
30-62 
30-65 


45-1 
43-6 

44-1 
42-6 


42-1 
39-1 
39-6 
38-1 


3-0 
4-5 
4-5 
4-5 


2-7 
2-3 
2-3 
2-2 


0-7 
1-0 
1-0 
1-0 


78 
68 
65 
69 


E. 

E. 

E. 

•S.E. 






10 
10 


6 
11 








M 


30-65 
30-56 


37-6 
42-6 


36-1 
37-6 


1-5 

5-0 


2-3 
2-1 


0-4 
1-1 


87 
66 


S.E. 
E. 






10 


10 








•1 


30-48 
30-43 
80-21 
30-14 


39-3 
43-6 
35-] 

41-1 


36-1 
40-1 
32-1 
38-6 


3-0 
3-5 
3-0 
2-5 


2-1 
2-5 
1-7 
2-4 


0-7 
0-8 
0-7 
0-8 


77 
74 
72 
81 


E. 

N.E. 
E. 
E. 






10 

i'6 


9 
8 




... 




Means, . 




30-48 


41-4 


3S-0 


3-5 


2-3 


0-8 


74 






... 




... ... 






4 

Caixton-Mor, 
No. 19. 

135 feet. 

Lat. 56" 5' N. 
Long. 5° 28' W. 




30-48 
30-57 

30 ; 65 


52-0 
37-6 

49-0 
41-5 


47-0 
360 
43-0 
39 


5-0 
1-5 
6-0 
2-5 


3-0 
2-2 
2-5 

2-4 


1-4 
0-4 
1-5 
0-6 


69 
87 
62 
81 


E. 

N.E. 

E. 

E. 


1-0 
1-0 
1-0 
1-0 




2- 


1 




6 
6 








M 


30-63 
80«56 


54-5 
42-5 


41-5 
41-5 


13-0 
1-0 


1-8 
2-9 


3-0 
0-2 


38 
92 


E. 
N.E. 


1-0 
10 








10 










30-48 

80 :i 

30-12 


45-5 
37-5 

47-5 


40-0 
36-0 
45-0 
85-0 


5-5 
1-5 
2-5 
1-5 


2-2 
2-2 
81 
2-2 


1-2 
0-4 
0-6 
4 


64 
87 
83 

87 


E. 
E. 
E. 

N. 


1-0 
10 
1-0 
1-0 







2 



10 
8 








OS, . . I 


30-45 


44-4 


40-4 


4-0 


2-4 


1-0 


75 




1-0 















BKIGHT CLOUDS ON A DAKK NIGHT SKY. 



27 



Station. 


Date. 




Hygrometer 
at 9 a.m. 
and 9 p.m. 


Hygrometrical 
Computed Results. 


Wind 
at 9 a.m. 
and 9 p.m. 


Clouds. 


Sunshine. 


a 
o 

O 


a 

"cS 

M 


Remarks. 


00 

00 

a 
p. 
< 


O OS 

* a 
S ■< 

gg 

s i 


a 
■>> 

A 




o . 

OS 

.2 3 

A 


a < 

i* ° 
> § 

■a ■■§ 
1 2 


it © 
~ t <X> _ 

HI 

;-. 3 Q 


111 


a 

s 


. O 

eg 

""* a) 

£ cr 

s.2 

^a 

o 


a 
A 


o 
i— i 
i 
o 

a 
o 

a 
< 


Eallabus, 
No. 20. 

71 feet. 

Lat. 55° 47' N. 
Long. 6° 15' W. 




ins. 
30-48 
30-53 
30-61 
30-62 


45" 
43- 

47- 
47- 


42° 

40- 
42- 
43- 


3° 

3- 
5- 

4- 


grs. 
2-7 
2-5 
2-5 

2-7 


gr- 
0-7 
0-7 
1-2 
1-0 


78 
78 
67 
73 


B. 

E. 
B. 
E. 


1-0 
1-0 
1-0 
9-0 






hrs. 








»{ 


30-61 
30-51 


49- 
45- 


41' 
40- 


8- 
5- 


2-1 
2-3 


1-9 
1-1 


53 
66 


E. 

E. 


9-0 
1-0 














10 | 


30-46 
30-35 
30-25 
30-12 


53- 
36- 

43- 
38- 


44- 
35- 
43- 

37- 


9- 

1- 

o- 

1- 


2-3 
2-2 
3-2 

2-4 


2-2 
0-3 

o-o 

0-3 


51 

91 

100 

91 


Calm. 
Calm. 
Calm. 
Calm. 


o-o 
o-o 
o-o 
o-o 














Means, . 




30-45 


44-6 


40-7 


3-9 


2-5 


0-9 


75 




2-2 














Gordon Castle, 
No. 21. 

104 feet. 

Lat. 57° 38' N. 
Long. 3° 2' W. 




30-56 
30-60 
30-64 
30-64 


45-5 

38-1 
44-8 
43-0 


42-6 
36-0 
40-0 
36-5 


2-9 
2-1 
4-8 
6-5 


2-8 
2-2 
2-3 
1-8 


0-7 
0-5 
1-1 
1-4 


79 
82 
67 
56 


S.E. 
S.B. 
S.W. 
S.W. 












'3 
o 




«{ 


30-65 
30-56 


48-9 
39-1 


41-0 
37-0 


7-9 
2-1 


2-1 
2-3 


1-9 

0-5 


53 

83 


S.W. 
S.W. 












Aurora. 


10 { 


30-47 
30-36 
30-24 
30-14 


37-0 
35-0 
42-8 
38-5 


32-1 
33-5 
39-3 
37-0 


4-9 
1-5 
35 

1-5 


1-6 
2-0 
2-4 
2-4 


1-0 
0-4 
0-8 
0-4 


62 
85 

74 
88 


S.W. 
S.W. 
N.W. 
N.W. 














Means, . 




30-49 


41-3 


37-5 


3-8 


2-2 


0-9 


73 
















New Pitsligo, 
No. 22. 

495 feet. 

Lat. 57° 35' N. 
Long. 2° 9' W. 




30-56 
30-60 
30-65 
30-67 


42-1 
39-0 
41-4 
35-6 


40-7 
38-0 
40-4 
35-2 


1-4 

1-0 
1-0 
0-4 


2-7 
2-5 
2-8 

2-4 


0-4 
0-3 
0-3 

0-2 


89 
92 
92 
96 


S.E. 

S.E. 
S. 

s. 
















>{ 


30-65 
30-58 


47-4 
36-8 


44-8 
36-0 


2-6 

0-8 


31 
2-4 


0-6 
0-2 


82 
93 


s. 

S.E. 
















•< 

i»{ 


30-48 
30-33 
30-23 
30-14 


38-3 
33-8 
37-3 
38-0 


37-3 
33-1 
36-0 
36-3 


1-0 
0-7 
1-3 
1-7 


2-5 
2-0 
2-3 
2-3 


0-3 
0-2 

0-4 
0-4 


92 
93 

89 

85 


S.E. 

S. 

E. 
N.W. 












0-03 




Means, . 




30-49 


39-0 


37-8 


1-2 


2-5 


0-3 


90 


















Inverness, 
No. 23. 

114 feet. 

Lat. 57° 28' N. 
Long. 4° 13' W. 




30-59 
30-55 
30-68 
30-79 


40-0 
47-0 
37 
44-0 


38-0 
45-0 
35-5 
43-0 


2-0 
2-0 
1-5 
1-0 


2-4 
3-2 
2-2 
3-0 


0-5 
0-5 
0-4 
0-3 


84 
86 
87 
92 


E. 
E. 
W. 

N.E. 










10 




10 
8 


2 
6 
4 
6 


a 
'8 

o 




«{ 


30-64 
30-57 


41-0 
43-0 


39-0 
41-0 


2-0 
2-0 


2-5 

2-7 


0-5 
0-5 


84 
84 


N.E. 
E. 







10 


11 



4 




10) 


30-46 
30-34 
30-27 
30-14 


38-0 
39-0 
38-0 
46-0 


37-5 
38-0 
36-0 
41-0 


0-5 
1-0 
2-0 
5-0 


2-5 
2-5 
2-2 

2-4 


0-2 
0-3 
0-5 

1-2 


96 
92 
83 

67 


S.W. 

S.W. 

N.E. 

E. 






10 


10 



4 

2 


6 
4 
6 

8 




Means, . 




30-50 


41-3 


39-4 


1-9 


2-6 


0-5 


86 




... 


... 











VOL. XXXII. PART I. 



28 



C. PIAZZI SMYTH ON 



Station. 


Date. 


f * 

O S5 

<3 3 

I; 

•- r ' 

«*_ 

£■5 
M 3 


Hygrometer 

:il 9 A.M. 
and'9 p.m. 


Hygrometrica] 
Computed Results. 


Wind 

at 9 a.m. Clouds. 
and !) p.m. 


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to 


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Remauks. 


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00 

p. 

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o 

a 
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Aberdeen, 
No. 24. 

66 feet. 

Lat. 57" 9' N. 
Long. 2° 6' W. 




ins. 
30-59 
30 '63 

30-68 
30-70 


45°8 
42-9 
44-5 
41-0 


43°2 
40-4 
41-3 
39-8 


2-6 
2-5 
3-2 

1-2 


grs. 
2-9 
2-6 
2-6 

2-7 


gr. 
0-7 
0-6 
0-7 
0-3 


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82 
76 
90 


S.E. 


0-2 




"i 
2 


hrs. 
3 

9 








«< 


30-68 
30-60 


39-7 
41-5 


36-8 
39-2 


2-9 
2-3 


2-2 

2-5 


0-7 
0-6 


78 
83 








8 
9 


10 










30-49 
30-36 
30-25 
30-16 


40-3 
38-2 
39-0 
42-6 


38-2 
37-0 
37-6 
39-1 


2-1 
1-2 
1-4 
3-5 


2-4 
2-4 
2-4 
2-3 


0-5 
0-3 
0-4 

0-8 


84 
90 
89 
74 


S'.E. 

N. 
N. 


i'-6 

1-0 
0-2 




10 

4 

10 

10 


10 








Means, . 




30-51 


41-6 


39-3 


2-3 


2-5 


0-6 


83 
















Aberdeen 

Meteorological 

Council 

Observatory, 

No. 25. 

Lat. 57° 9' N. 
Loug. 2° 6' W. 




30- 
30- 
30- 

30- 


43-6 
41-6 
43-2 
39-5 


41-7 
39-4 
40-4 
38-6 


1-9 
2-2 
2-8 
0-9 


2-8 
2-5 
2-6 

2-6 


0-5 

0-5 

0-7 
0-2 


85 
84 
79 
93 


















M 


30- 
30- 


40-2 
40-7 


33-6 
38-9 


6-6 
1-8 


1-5 

2-5 


1-4 
0-5 


54 

86 


















10 { 


30- 
SO- 
SO- 
SO- 


39-7 
38-9 
377 
41-1 


37-7 
37-4 
36-7 
38-2 


2-0 
1-5 
1-0 
2-9 


2-4 
2-4 
2-4 
2-3 


0-5 
0-4 
0-2 
0-7 


84 
88 
92 

78 


















Means, . 






40-6 


38-3 


2-4 


2-4 


0-6 


82 
















Glasgow 
Mbtboeoloqioal 

Council 

Observatory, 

No. 26. 

Lat. 55° 53' N. 
Long. 4 J 18' W. 




30- 
30- 
30- 
30- 


45-0 
42-9 
43-4 
42-0 


42-8 
39-9 
40-4 
39-3 


2-2 
3-0 
3-0 

2-7 


2-9 
2-5 
2-5 
2-5 


0-5 
0-7 
0-7 
0-6 


84 
78 
78 
80 


,. ._ 
















>{ 


so- 
so- 


42-8 
41-8 


40-0 
39-8 


2-8 
2-0 


2-5 
2-6 


0-7 
0-5 


79 
86 




















30- 

so- 
so- 
so- 


39-2 
42-7 
33-0 
40-0 


36-8 
40-1 
33-0 
37-6 


2-4 
2-6 
0-0 
2-4 


2-2 
2-6 
2-2 
2-3 


0-6 
0-6 

o-o 

0-6 


81 

81 

100 

81 


















Means, . 






41-3 


39-0 


2-3 


2-5 


0-6 


83 


















Rotax Observa- 
tory, Greenwich 
(London). 

No. 27. 

— feet. 

Lat .'.l 29* N. 
Long. J V 


«{ 
'< 


30- 


48-4 

II-:; 

51-0 
15-7 


46-3 
42-0 
47-4 
43-0 


2-1 
2-3 
3-6 
2-7 


3-28 

2-77 
3-22 
2-83 


0-56 
0-56 

O-.I.S 

0-71 


85 
82 
76 
81 


















», 


30- 


53 -0 
44-9 


49-2 
42-2 


3-8 
2-7 


3-44 
2-75 


1-06 
0-64 


75 

80 












::: 1 ::: | 


9 {!*>• 

10 ; »; 


48-3 
410 
16-9 
43-8 


45-1 
39-4 

li:i 
41-2 


3-2 
1-6 
2-6 
2-6 


::-(io 
2-59 
2-98 
2-66 


(ISh 

0-42 
0-71 

0-02 


78 
87 
82 
SO 












:;; i ;:; 




08, . 


j... 


46-7 


44-0 


2-7 


2-95 


0-71 


81 










... i ... 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 29 



APPENDIX II. 

Projections of the preceding Observations, see Plates II. to IX., viz. : — 
Plate II. Map of the Scottish Meteorological Stations referred to. 



Plate III. 


Observations at Edinburgh. 






Do 


Wanlockhead. 






Do. 


North Esk Eeservoir. 






Do. 


Braeinar. 




Plate IV. 


Do. 


Douglas Castle. 






Do.. 


Stobo Castle. 






Do. 


Marchmont, Berwick. 






Do. 


New Pitsligo 




Plate V. 


Do. 


Stronvar. 






Do. 


Moffat. 






Do. 


Haddington. 






Do. 


Greenock. 




Plate VI. 


Do. 


Cupar (Fife). 






Do. 


Dalkeith. 






Do. 


Callton-Mor. 






Do. 


Smeaton. 




Plate VII. 


Do. 


Balloch Castle. 






Do. 


East Linton. 






Do. 


Paisley. 






Do. 


Eallabus. 




Plate VIII. 


Do. 


Glasgow, No. 1. 






Do. 


Glasgow, No. 2. 






Do. 


Aberdeen, No. 1. 






Do. 


Aberdeen, No. 2. 




Plate IX. 


Do. 


(Greenwich, Royal Observatory, London, 


communicated.) 




Do. 


Gordon Castle. 






Do. 


Inverness. 





[Appendix III. 



30 



C. PIAZZI SMYTH ON 



APPENDIX III. 

I. Numerical Tables of Hourly Observations of Temperature, Depression of "Wet-bulb, and 
Hygrometrical Deductions for 

Aberdeen, 
Glasgow, and 
Greenwich. 



II. Plates X. to XIV. of Graphical Projections of the preceding Hourly Observations, viz. :- 

Plate X. Temperature Curve at Aberdeen. 
Do. Glasgow. 

Do. Greenwich. 

Plate XL Depression of "Wet-bulb Therm, at Aberdeen. 

Do. do. Glasgow. 

Do. do. Greenwich. 

Plate XII. Weight of Vapour in 1 cubic foot of Air at Aberdeen. 

Do. do. Glasgow. 

Do. do. Greenwich. 

Plate XIII. Vapour required to saturate 1 cubic foot of ah' at Aberdeen. 

Do. do. Glasgow. 

Do. do. Greenwich. 



Plate XIV. Humidity Curve at 
Do. 
Do. 



Aberdeen. 

Glasgow. 

Greenwich. 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 



31 



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3-i C. PIAZZI SMYTH ON 



APPENDIX IV. 

1. Greenwich Testimonies as to Cosmical Accompaniments of Aurora being deficient 
on April S, 1882, and April 30, 1883. — Letters 1 and 2. 

Royal Observatory, Greenwich, 
London, S.E., May 12, 1883. 

Dear Sir, — In regard to unusual phenomena on 1882, April 8, and 1883, April 30, as compared 
•with adjacent days, I am requested by the Astronomer-Royal to inform you as follows : — 

The magnetical registers (Declination, Horizontal Force, and Vertical Force) indicate nothing 
unusual, neither do the Meteorological (Barometer, Thermometer, Electrometer). 

Wind 1882, April G to 10, steady EKE and N.E. throughout the greater part of the five days, 
changing on afternoon of April 10. 

Wind 1883, April 29 to May I. Change on April 30 from K to S.W. at 4 h , and from S.W. 
to E. at G^ h . On April 29 change in opposite direction about same times. On May 1, steady 
N.E. wind. 

1882, April 8. Brilliantly fine and cloudless throughout, similar on April 6 and 7, very little 
cloud on April 9, cloudy but fine on April 10. 

1883, April 30. A very similar day (in all respects) to May 1. 

I am, Dear Sir, 

Yours very truly, 

(Signed) WlLLIAM ELLIS. 



Prof. C. P. Smyth. 



Royal Observatory, Greenwich, 
London, S.E., May 14, 1883. 



Dear Sir, — With reference to your inquiry as to whether there was anything unusual on the 
Solar photographs of 1882, April 8, and on 1883, April 30, as compared with photographs taken 
on neighbouring days, the Astronomer-Royal requests me to say that there are no noteworthy changes 
in the spots shown on pictures taken on 1882, April 7, 8, and 9. Small spots were constantly 
forming or disappearing, but nothing unusual is shown. 

The picture taken on 1883, April 30, shows a group of several very small spots which disappeared 
before 1883, May 1. Two small groups not visible on 1883, April 30, are shown on the picture 
taken on May 1. The changes are not at all unusual in character or amount. 

I am, Dear Sir, 

Yours very truly, 

(Signed) E. Dun kin. 

Prof. C. Piazzi Smyth. 



2. Of the Aurora said to have been observed at 1 Station out of 24 in Scotland 

on April 8, 1882. 

Letter from the Gordon Castle Observer to Mr Buchan, Secretary Scottish Meteorological Society. 

Dear SIR, — T am in receipt of your note inquiring about "Aurora" entered in my notes of daily 
readings in 1882. I have looked up the Schedule, and find there are no particulars dated; simply 
Aurora. The time is too far back to bring my memory to it, but I see by the readings under, that 
it had been the precursor of a considerable depression of the atmosphere at the period. 

I am, Sir, 

Yours faithfully, 

(Signed) JOHN WEBSTER. 



BRIGHT CLOUDS ON A DARK NIGHT SKY. 



35 



3. Of Aurora Spectroscopically observed in Edinburgh at the Astronomers' 

House in 1S82 and 1883. 

The concluding remark in Mr Webster's letter, that the date of his stated Aurora, April 8, 1882, 
was followed by a considerable depression of the atmosphere, is perfectly true ; for the record of 
Barometer (uncorrected), wind, rainfall, and clouds, kept at the Royal Observatory, Edinburgh, in 
connection with Time signalling, runs thus from April 5 to April 15, 1882 : — 



Day. 


Barometer. 


Wind. 

Miles per 

hour. 


Wind. 
Direction. 


Rainfall, 
Depth of. 


Clouds. 
to 10. 


April. 


Inches. 






Inch. 




5 


29-99 


3 


N.E. 


•000 


10 


6 


30-10 


2 


N.E. 


•013 


6 


7 


3023 


4 


N.E. 


■000 





8 


30-22 


2 


N.E. 


•000 





9 


30-02 


2 


N.E. 


•000 


3 


10 


29-77 


3 


N.E. 


•000 





11 


29-58 


2 


N.N.E. 


•000 


10 


12 


29-45 


3 


S.S.E. 


•000 


9 


13 


29-06 


8 


E. 


•035 


10 


14 


28-83 


10. 


N.E. 


•424 


10 


15 


2929 


1 


N. 


•230 


10 



That circumstance, however, does not prove that the luminosity Mr Webster observed in the sky 
at Gordon Castle was a real Aurora. It certainly could not have been one of the grander Aurora?, or 
it would have been noted at some of the 23 other stations ; would have imprinted itself indelibly on 
the observer's memory, and would have marked itself on the continuous photographic curves of the 
magnetic needles at Greenwich. 

Whether it was, however, a faint Aurora, or perhaps some other luminous manifestation, I do not wish 
to suggest a word either for or against ; but if the observer could have said that he spectroscoped it 
with a pocket spectroscope, and saw the Auroral Citron line, — I should have accepted the testimony 
immediately. For I myself have never yet spectroscoped any decided Aurora, without its showing 
that line ; and have never seen that line in any other light, though I have, on one occasion, elicited 
the line out of a full-Moon, mid-night sky, when at the time there was no appearance of Aurora or 
any of its usual accompaniments, — but where, an hour before, there had been some unmistakable 
needle-shaped jets and darts of its light on the Northern horizon. 

The opportunities I have had for good numerical observations of the Auroral spectroscopic line, 
during the last 1 5 months have not been many ; but may form a useful addendum to the present 
paper, — as follows : — 

O October 22, 1882, at ll h p.m. ; the moon ten days old, and the sky bright with moonlight; 
Aurora seen as a faint but regularly-shaped arc on the N.W. horizon ; spectrum place of its Citron line 
= 45 511 of Wave Number per Brit. Inch. 

h October 28, 1882, at midnight; past full-Moon; sky clear and frosty. No Aurora visible to 
the naked eye at the time, though there had been earlier in the evening. The place of Aurora line, 
doubtfully observed, came out 45 350 (?) W.N. Place. 

$ November 14, 1882. Aurora lasted through much of the night, but chiefly behind clouds. 

? November 17, 1882. A grand Aurora; but barely seen here by reason of clouds, smoke, and 
direction. 

h November 25, 1882, ll h 30 m p.m.; Moon just past the full. No Aurora to naked eye, 
but its line was clearly seen in the spectroscope, followed by a broad band of continuous spectrum of 
the Moonlight. Place of the line observed at 45 593; while the continuous band of Moonlight 
began at 46 610, culminated in intensity near 48 200, and ended gradually near 52 610 W.N. Place. 

([ March 26, 1883, at 10 h p.m.; a rather bright Auroral arc northwards, its central portion 
rising 10° or 15° high, and having dark shade underneath. Its Citron line's place measured 45 558 
W.N. Place. 

$ March 27, 1883, at 10 h p.m.; a long low quiescent, or blandly-shining faint arch of Aurora 
on the northern horizon. Its Citron line's spectrum place measured 45 542 W.N. Place. 

VOL. XXXII. PART I. F 



3G BRIGHT CLOUDS ON A DARK NIGHT SKY. 

This latter was the hest Auroral manifestation I have seen this season. Many others I believe 
have been noted in Sweden and Norway ; but those countries seem to be situated over one of the 
Earth's invisible quabi volcanoes, or rather perhaps " maelstroms " of Aurorae ; so that as Professor 
Angstrom noted many years ago, and Professor Lemstrom more recently, there is sometimes an Auroral 
phosphorescence there on everything about them, air, earth, ice, and water. 

Such phosphorescence, however, as Professor Lemstrom has well remarked, is recognised by its 
giving to the spectroscope the well-known Citron Aurora line, whose place is close, according to my 
observations, to 45 550 W.N. Place. 

But other kinds of phosphorescence, so far as I have observed them, give only a band of continuous 
spectrum in the green and glaucous regions, necessarily more refrangible than the Aurora line ; or 

Stick phosphorus in a chamber, has the maximum brightness of its 

broad, faint, band at . . . . . 49 000 W.N. PI. 

Animal phosphorescence at sea, has the similar centre at 

Carbo-hydrogen blue flame, when too faint to show its individual 
lines, has its chief brightness near .... 

The Zodiacal light has the same, at or near 

Twilight has the same, at or about .... 

While Moon light, as above, has it at or near 

The last three therefore can hardly fail to be of one and the same Solar origination ; but the two 
first are quite different from them ; and still more different are they from the chief Auroral line, both 
in appearance and spectrum place; while the third suits our faintly bright night clouds of April 8, 
1882, with' a broad slit perfectly. 



49 000 W.N. 


50 300 


49 200 


48 150 


48 150 


48 200 






Trans^o^SocTldin* 



Vol. XXXII. Plate II. 



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( 37 ) 



III. — Note on the Little b Group of Lines in the Solar Spectrum and the New 
College Spectroscope. By C. Piazzi Smyth, Astronomer-Royal for Scot- 
land. (Plate XV.) 

(Read June 1883). 

Every spectroscopist is perfectly aware that the group of dark Fraunhofer 
lines in the Solar Spectrum, known as " little b," is composed of the biggest, 
broadest, most colossal lines in all the brighter part of any and every spectrum 
depending on Sunlight, whether direct from the Sun or reflected from the earth's 
atmosphere, the Moon, or any of the planets. 

How the apparent misnomer came about, was not on the principle of the 
biggest gun ever made by our military, being termed "the Woolwich infant ; " 
but because after Fraunhofer had spaced out the spectrum into nearly equal 
lengths, so far as the majority of the chief lines allowed, and called them by 
capital letters, beginning with great A in the ultra red and ending with great 
H in the ultra violet, — he then began again at the red end, and marked all the 
notable intervening lines by small letters. Whence it came about that those 
sometimes very imposing bands of telluric water- vapour lines " little a " are 
found between great A and great B ; and those grand and truly solar lines 
in the green, little b, are found, by accident as it were of Nature, between great 
E and great F. 

In the smaller class of pocket spectroscopes and on the faint light of the 
Sky, observers merely recognise two strong lines ; the first from the red end is 
b 1 , and the second, considerably thicker, is b 2 * A very little increase of power, 
however, easily shows b 2 to be composed of two lines, b 2 and b 3 ; and Fraun- 
hofer himself had announced it. But that such b 3 was still further composed 
of two lines was I believe first discovered by Professor Swan, and published in 
our Transactions as part of his now classical spectrum paper of 1855 and 1856. 
For therein (vol. xxi. p. 427) he mentions most clearly — though calling our 
b\ b 2 , b 3 by the names b, b\ b 2 that " on the 20th of May, about 7 h 10 m p.m. 
when the sun was rather low on the horizon, but free from clouds, he observed 
with a magnifying power of 21 (on his large theodolite telescope, directed to a 
single prism of 60°) the line b 2 (our b 3 ) to be very finely but distinctly double ; 
so that," he adds, " the group consists of 4 lines " (our b 1 , b 2 , b 3 , and b 4 ). While 
on page 426 he had already expressed his admiration for the group " as being 
one which, whether we regard the singular configuration or the strength of the 
lines which compose it, is perhaps the most notable in the solar spectrum." 

In the Philosophical Transactions of the Royal Society (London) for 1860, 

VOL. XXXII. PART I. G 



38 C. PIAZZI SMYTH ON THE 

there is a picture by Sir David Brewster and Dr Gladstone confirming these 
four grand lines of little b, and adding some thinner intervening lines and faint 
broad bands. But before that could produce much effect on men's minds, it 
was utterly eclipsed by the far grander Solar Spectrum map, first of Prof. 
Kirchoff, and then of Professor Angstrom, whose exquisitely engraved, and 
certified, map still remains for many purposes the Normal Solar Spectrum Map 
of all the human race. 

Now let us take a new start from that last map, date 1868, in order to 
ascertain something of our present degree of knowledge touching the visible 
characteristics of these four remarkable lines ; for however many thinner ones 
there may be, the principal members of the group are four only, and have over- 
whelming importance. Two of these moreover, viz., b 1 and b 2 were represented 
by Angstrom physically different from the others, by slightly bordering them 
with haze. 

In 1875 the Royal Society published a map in their Philosophical Transac- 
tions, where they represented (though by a very exceptional kind of symbolic 
marking, looking really like something else very different but very important if 
true) these haze borders of b 1 and b 2 as still broader ; but made 6 3 and b i , pale 
in a high, dark in a low, sun, as though they were atmospheric or telluric lines, 
which they certainly are not. 

In 1880 M. Fievez, in the R. Observatory of Brussels, represented several 
lines hazy, though he left £ 4 quite sharp and black. 

But in the same year Professor Vogel, of the Astro-Physicalischen Observa- 
tory at Potsdam in Prussia, and armed with a new spectroscope of immense 
power, published a very superior spectrum map wherein he represented b l , 6 2 
and ¥ all equally and very broadly hazy, but kept b B quite sharp, well defined 
and black, besides adding many thin lines, some single and others double. 

In the following year at Madeira I had the opportunity, besides confirming 
Professor Vogel on all the four great lines, of adding thereto the further physi- 
cal distinction that the lines themselves, inside the envelopes of haze of b 1 , b 2 
and £> 4 were all of a peculiarly faint material ; and of presently still further 
discovering both that the & 4 line, within the compass of its own haze, was 
double ; and that 6 3 , without any haze, appeared not actually double, but to 
promise certain resolvability into it, had my apparatus been only of a slightly 
better order. 

At the time I could hardly believe my eyes ; but have learned since then 
that the duplicities of 6 3 and 6 4 had been just previously to that date ascer- 
tained with some of the splendid spectroscopes in America ; as they were also 
subsequently by a second very powerful spectroscope built up, and employed 
by M. Fievez at the Royal Observatory, Brussels, in 1882. 

But perhaps I am going on too fast ; for certain learned parties, to whose 



LITTLE b GROUP OF LINES IN THE SOLAR SPECTRUM. 39 

extensive knowledge implicit respect has hitherto been generally paid, have not 
yet taken any notice of either M. Eievez or the American observers. A 
particular case of such neglect is to be found in the new, or third edition, of 
Dr Schellen's German work on " Spectrum Analysis " published during the 
present year, 1883, in 2 volumes, and an atlas filled with excellent engravings. 

The number of different spectroscopes illustrated in those volumes is legion. 
But amongst them all, the highest opinion seems to be entertained for the 
spectroscope of Professor Vogel, already alluded to. The instrument was 
made by the celebrated M. Schroder of Berlin, contains 6 large compound 
prisms of heavy glass, with powerful telescope, collimator and automatic move- 
ments to match. It is represented accordingly with pride in three pictures on 
pp. 243, 244 and 245 ; while on p. 247, to prove beyond doubt how advanced 
are its powers, a pair of diagrams of the little b group are given ; first, as 
they were represented by Angstrom in his day ; and second, as they are 
now seen by Professor Vogel. But though the latter, as I have already stated, 
introduces several more thin lines, he leaves the four classic members of the 
little b group, as given by Angstrom at the early spectroscopic date of 1868, 
untouched ; for Dr Schellen, by some inadvertence having imparted haze to 
Angstrom's view of 6 4 , has destroyed (on his own plate) the rightful claim 
of Professor Vogel to that physical discovery. 

Now let us contrast that state of things with some observations I have just 
been able to make in Edinburgh through the sunshine there, all smoky as it 
unhappily is, at No. 15 Koyal Terrace, but Avith an admirable spectroscope, kindly 
left in my hands for a few weeks by Professor P. G. Tait, — after he had, by a 
marvellous chance, been able to acquire it for the Natural Philosophy Labora- 
tory of the Edinburgh University. It is of English make, by Messrs T. Cooke 
& Sons of York, but constructed for the late eminent Belgian scientist, Dr Van 
Monckhoven, on a plan arranged between himself, Mr Lockyer and Messrs 
Cooke ; though he had hardly received it when sudden death by angina pectoris 
cut short his splendidly energetic and promising career, to the terrible grief of 
his family and friends. The instrument thrown thus open to purchase again, 
was sent here by Messrs Cooke, and I could not but admire exceedingly the 
compactness of its arrangement, by which it was enabled in a remarkably small 
compass and with absolute directness of vision throughout the whole spectrum, 
to employ virtually any number of prisms from 2 to 20. Every prism too 
being " simple," and of white flint glass ; a feature in happy opposition to the 
compound prisms of brown or green flint glass, cemented to crown-glass anti- 
prisms, which are far too frequent favourites elsewhere. 

But how did the Cooke spectroscope acquit itself, when tried with the 
maximum number of its prisms, and highest magnifying power of eye piece ? 
I was over and above delighted to find that it focussed more sharply than any 



40 C. PIAZZt SMYTH ON THE 

spectroscope I had ever used ; and on bringing in our old friends of the little b 
group, there was not only all that Dr Schellen and Professor Vogel have 
recorded for the latter— not only too all the physical features which I had noted 
with difficulty at Madeira, — but there were b z and b i , each of them as clearly 
doubled, and their components clean separated, as any observer could possibly 
desire. Of b z one line was shown to be much stronger than the other, but 
equally sharp ; while of b A one line, the stronger also of the pair, was evidently 
hazy, and just as accurately concentric with that cloud of haze, as were the 
old b 1 and 6 2 with regard to their clouds of haze ; but the new and weaker 
component of 6 4 was evidently excentric to the haze of 6 4 ; a further test now 
of performance, but whose additional utility will presently appear. 

So far then as mere optical definition was concerned, nothing could be more 
satisfactory, or rather I should say transcendent, than this trial of the new 
College spectroscope on the little b group ; though it had been preceded in its 
detection of duplicities merely, by the American observers, and also by M. 
Thollon in France, and M. Fievez in Belgium. But those gentlemen have 
not, so far as I know, taken the further step of investigating chemically and 
physically the ultra nice points of optical discovery which they have added to 
the b group. 

I do not of course by this allude to what every one may read in Angstrom's 
admirable normal map, as to b 1 , b 2 and & 4 , all of them now known to be endued 
with a remarkable haze, being the reversals of magnesium metal burning in the 
Sun, and 6 3 , so strikingly without haze, being a similar representative of iron ; 
— but to this further detail, that under and coincidently with 6 4 , Angstrom 
placed an iron, as well as a magnesium line ; and under b 3 , a nickel, as well as 
an iron line. Or, as his followers are delighted to assert, 6 3 and b A are basic 
lines ; viz., one line standing as a base for two metals. The principle therefore 
of any such basic line represents a new chemistry, where two earthly elements 
are, by long roasting in Solar heat, resolved into one element, forming a 
common base to them both. So that certain reputed simple and original 
elements of the chemists hitherto, are really compound bodies ; and the list of 
elements in the Sun, is shorter than that which is accepted on the earth. 

It is something of a check to that system, to he enabled to say from mere 
optical observation, that in the two instances in little b, where basic lines had 
been thought to be met with, superior spectroscopes have shown there are two 
lines in each case ; but much more than that is necessary for full proof ; for 
who can be certain that any two given spectrum lines seen very close together, 
in place of representing a mere chance, or optical, coincidence of two perfectly 
unconnected elements' lines, may not be a physically double line of some one 
metal. 

I have therefore been trying the Cooke Spectroscope on this point, by 



LITTLE b GROUP OF LINES IN THE SOLAR SPECTRUM. 41 

deflagrating before it with condensed induction spark the several metals con- 
cerned. My apparatus for that purpose is unfortunately very primitive and 
weak, not more than l*5-ineh sparks in air, and 1 quart Leyden jar to condense ; 
but by placing the spark in front of the slit, obtaining the solar spectrum 
between the points of the sparking metals, and correcting by eye for the neces- 
sarily curved spectral lines of 20 simple prisms, — certain definite results were 
obtained on some of the points required, as thus — 

(1) For Magnesium. The metal spark line corresponding to ¥ is just as 
certainly a single line, as those corresponding respectively with b 1 and b 2 ; and 
further it falls on the second, more refrangible, and stronger component of the 
Solar & 4 , quite suitably to its hazy physical appearance in the Sun. 

These three Magnesium spark lines moreover form an ordered triple, 
remarkably like the Oxygen triples which I announced to the Society some 
two years ago, in so far that the 2nd and 3rd are closer together than the 1st 
and 2nd, and the intensities of each go on decreasing from 1st to 2nd, and from 
2nd to 3rd, but the arrangement is on a far grander scale. 

(2) For Iron. Two of its spark lines appear in the field of view in places 
evidently belonging to b 3 and 6 4 in a general way ; but they are both sadly 
faint, i.e. in my weak sparking apparatus. However the stronger one is 
remarkably sharp and may be certainly said to coincide with the first, or least 
refrangible component of 6 4 in the Solar spectrum ; which is that one which 
simple observation had already shown to be excentric to the characteristic 
magnesium haze. With not by any means so much certainty, unfortunately, the 
fainter iron line may be said to coincide with the stronger of the two recently 
discovered components of the Solar b s . 

(3) For Nickel. Here the result was poor to utter disappointment ; the 
tabular Nickel line concerned has only an intensity of 2 attributed to it, against 
many that are classed as 10, by the great spectroscopists with powerful 
apparatus ; and it appeared to me to deserve even less. Indeed I had only to 
wander a little further on into the blue regions of the spectrum to find Nickel 
lines there that were a pleasure and a certainty to compare with Solar lines ; 
but the particular Nickel line in or near b 3 was so faint as to be utterly hazy and 
undecided ; wherefore I must relegate this question of the 6 3 supposed basic line 
to those who can produce brighter sparks of Nickel and Iron than I can. 

And there is another point touching Nickel that I would also recommend 
to their earnest attention. Every one has heard of the Nickel line between the 
two D lines of the Solar spectrum ; and many persons will have read in Dr 
Marshal Watt's most useful Index of Spectra that both Thalen and 
Kirchoff have assigned their maximum for intensity, or 10, to that Nickel 
line. Being desirous therefore to see what such a grand line would look like in 
the Cooke spectroscope when sparked by my apparatus, I brought it into the 



42 C. PIAZZI SMYTH ON THE 

field, together with the Sun spectrum ; but behold, although it was much 
clearer than the little I s Nickel line, it was yet a very poor thing ; so poor, that 
I wandered off into the Citron regions, amongst the groves of hazy air lines, to 
see if something better could not be found there ; and sure enough I stumbled 
almost immediately on a magnificent line, a line which for brightness, beauty 
and definition was far beyond everything else in the field of view, though that 
was a pretty full one too. It proved to be the line at 46 380 W.N. Place, which 
Dr Watts has entered in his tables on the authority of both Thalen and 
Kirchoff as of intensity only equal to 6, when the trifling line between D 1 and 
D 2 was called by them 10. 

On turning to Angstrom's Normal Solar map with its chemical references, 
I was encouraged by finding the D Nickel line and its Solar representative also, 
far fainter than the 46 380 W.N. line of Nickel and its Solar reversal. But on 
still further referring to that most able observer M. Lecoq de Boisbaudran, he 
represents the 46 380 line, as the very maximum, or the a, of the whole Nickel 
spectrum ; gives no place to the D Nickel line at all ; and only the faintest 
imaginable marking to the Nickel line in the place of b 3 . His deflagrating 
method was however different ; for he used simple, uncondensed electric sparks, 
and employed them not on metal points, but on a solution of a salt of the 
metal. Perhaps too, bearing in mind the extreme modesty of his " spectro- 
scopic installation," it is wrong to refer to him, — master hand though he 
undoubtedly is, so far as it accords with his plan to go into any subject, — for 
more than the testimony he gives to the magnificent lustre of the a line at 
46 380 W.N. Place. So that the only remaining anomaly, but a most important 
one, to be cleared up by those who have plenty of electrical energy at their 
command and a good spectroscope, is, the immense intensity attributed to the 
D Nickel line by MM. Thalen, Kirchoff and Watts ! Is there a numerical 
error there, or is that line capable of peculiar intensification with increased 
electric temperature % 

But meanwhile though I may have failed in that inquiry, what an extension 
of the powers of pure and simple spectroscopic observation (when we have 
light enough) does not the new College Spectroscope already exhibit ! 

A few years ago some of our best men thought the ne-plus-ultra of accurate 
observing had already been reached with the Dispersion of a single prism of 60° 
and magnifying power on a telescope of about 20 : for after that, they found 
that whatever was gained in Dispersion by adding a second or third prism, was 
lost by bad definition. But here, thanks to the super-excellence of our British 
optical house, Messrs T. Cooke & Sons of York, no less than 20 prisms are 
virtually employed, and the limits of fine definition, even when tested by high 
magnifying power, are not yet reached. 

All that Dispersive power too, and all that Definition are perfectly necessary 



LITTLE b GROUP OF LINES IN THE SOLAR SPECTRUM. 43 

in the present day. For as this Note must have shown, if it has shown anything, 
the most radical and fundamental questions in all Chemistry and the very 
constitution of the Cosmos depend upon the most recently elicited and minutest 
of all the phenomena yet observed. 

P.S. September 28, 1883. 

The above position will become still more distinct on considering two sets of first rate observations in tbis 
part of the Spectrum, contained in tbe Proceedings of the Royal Society (London), and the present paper should 
by no means be allowed to close without honourable mention of both of them. 

The first to be noticed of these sets, is by Professors Liveing and Dewar, working in the magnificent 
Cavendish Laboratory at Cambridge ; and writing at p. 229 of said Proceedings for May 1881, of b 3 , that it is 
" a close double, but the Iron is less refrangible than the Nickel, line." 

While of i 4 they state with greater fulness :— 

" By examining the arc of a battery of 40 Grove cells, or that of a Siemens' machine, taken in a crucible of 
lime under the dispersion of the spectrum of the fourth order given by a Eutherfurd grating of 17,296 lines 
to the inch we are able to separate the iron and magnesium lines which form the very close pair ¥ of the solar 
spectrum. Either of the two lines can be rendered the more prominent of the pair at will, by introducing iron 
or magnesium into the crucible. The less refrangible line of the pair is thus seen to be due to iron, the more 
refrangible to rnaonesium. Comparison of the solar line and the spark between magnesium points confirms 
this conclusion, that the magnesium line is the more refrangible of the two." 

This accords well enough with, and indeed overshadows, my imperfect experiments in Edinburgh. But 
what are we to think, on turning to p. 443 of the same Society's Proceedings for the earlier date of March 20, 
1879 where that distinguished spectroscopist Mr Norman Lockyer, working with all the resources of the 
Government Department of Science and Art at South Kensington, implies, of ft 3 , that there is no Iron there, 
only Nickel ; but of ¥, that there are besides Iron and Magnesium, no less than 9 other metals, viz., Mo, W, Co, 
Mn, Ca, Li'?, Na 1 ?, Cu, and Al, coincident with it. 

The beginning of some explanation of this difference undoubtedly is, that at the time of his observation, 
the accomplished observer had not heard that both 6 3 and ¥ were double lines, and had not a spectroscope of 
sufficient power to show them so. 

The second part of the explanation is probably due to the admission in the last par. of p. 442, that 
compulsory "rapid surveys of tbe arc spectra of most of the metallic elements" have led to approximate, being 
sometimes assumed as exact, coincidences. 

This is an almost necessary feature in the earlier stages of any inquiry ; but now that we are happy to 
learn on one side, that Mr Lockyer has come into possession of one of Professor Bowland's (U.S.Am.) grand 
concave Gratings, and on the other, know that the Natural Philosophy Laboratory of the Edinburgh University 
possesses the Monckhoven-Cooke Spectroscope, together with a 4-horse power Gas-engine, Dynamo, Grand 
Induction-Coil and Condenser to suit, — we may expect something very important from either one or both those 
parties revising that list of so many metals supposed, four years ago, to have one common meeting place 
in the Spectrum. 

C. P. S. 

EXPLANATION OF THE PLATE REPRESENTING THE COURSE OF DISCOVERY 
TOUCHING: THE LITTLE i GROUP IN THE SOLAR SPECTRUM. 

This plate is rough and rude to a degree, and that is partly intended ; because, to attempt 
to reproduce the infinite refinement of shades, tints and lines shown by Nature in the Solar 
spectrum, belongs more to the department of artistic beauty, than scientific work ; and already 
every high Solar scientist has utterly discarded the trouble and expense of introducing that 
leading element of the Spectrum's beauty, colour, into his maps ; and has taken that very 
stron^ step towards a symbolic, rather than realistic, representation, partly on account of the 
absence of colour-pigments from his paper enabling him to bring out the more useful black or 
grey of the Fraunhofer lines with greater force and more ease of recognition. 

But even then, in mere black and white, the question comes up once again, should we 
attempt to reproduce every such refinement the spectrum itself shows, and in the manner in 
which it appears there, — which would necessitate the most ultra microscopic engraving on 



44 C. PIAZZI SMYTH ON THE LITTLE b GROUP OF LINES, ETC. 

copper or steel plates ; — or shall we adopt a short, easy, symbolic method by which in the tenth 
of a second we can make a mark anywhere, on paper as well as copper-plate, signifying merely, 
or standing for, such and such an artistic, or realistic, effect ? 

A splendid example of the former method is to be seen in M. Coknu's fine engravings of 
the ultra-violet portion of the Solar Spectrum ; for there, thin lines are successfully repre- 
sented of every degree of shade from lightest to darkest ; but without the mechanical means by 
which they are executed appearing to the eye, until reinforced by a powerful magnifying glass ; 
and they are then seen to be the effect of minute dots more or less closely packed, and without 
ever recurring to " the vulgar expedient " of ruling an actual line, in one uniform degree of 
blackness. When any person donates the science of his time with such a Solar spectrum map, 
whether in whole or part, the public ought to be very grateful to him ; and it is to be hoped 
they are so, in this case, to M. Cornu, the distinguished Parisian scientist, for his unmatched 
portraiture of " the region of fluorescence." 

But the daily work of the world requires an interim employment of some easier method, 
something akin to writing by the letters of the alphabet as signifying sounds, in place of paint- 
ing pictures of the things intended. One method already extensively in use and much to be 
commeuded, is to express the different degrees of darkness of a Fraunhofer line, whatever 
the breadth, by different heights or depths of the line ; and this it will be seen I have availed 
myself 'of in several instances. 

The same principle may be applied to the shadings by which bands are represented in the 
Spectrum. Shadings of some kind are necessary there with the very faint bands, to prevent 
straining the symbol too far ; which would result, if we had only the device of shortening the 
height of a band in positive black ink, to represent an ultra faintness of shade. Such shade 
being, in reality, at the telescope, just as high necessarily as any of the blackest lines, 
because they are all reproductions of one and the same slit in front of the spectroscope. 

Faint bands therefore have long since been generally represented by a shading of thin 
parallel lines ; and the method is unequivocal when the lines are ruled in any direction except 
that, in which they might be repetitions of the slit of the Spectroscope, or stand for separate, 
independent, thin Fraunhofer lines. 

Hence I have represented the hazy borders of the b lines, by either horizontal, or 45° inclined 
lines, and no spectroscopist will take them, or the knots in them, as anything else than 
symbols of shade. It is necessary too, to be very particular on this point, because the Royal 
Society, London, in both its Philosophical Transactions and Proceedings, has most pertinaciously 
set, and is still setting, the opposite example of representing shade in the spectrum, by thin lines 
ruled parallel to each other and in the direction of the slit ; so that when many and many a 
close double, or treble, or quadruple Spectral line appears in a Eoyal Society engraved 
Spectrum plate, it may mean, either that their observer did see a double, or treble, or quad- 
ruple line in that place ; or, that he only saw a faint, unimportant haze. 

Finally in our present plate, one mere difficulty has to be compassed ; for it is to be an 
historic memento, from the earliest spectroscopic times to the latest. In my last year's publica- 
tion, "Madeira Spectroscopic" I attempted to meet a similar case, by representing every 
observation, of whatever date, on one and the same scale. But I have been told that some 
persons do not like the necessarily resulting effect of that plan, in so far as it makes the earlier 
observations, taken with very small dispersive power, look colossal in coarseness. In the 
present case therefore, I have decreased that appearance by adopting a smaller and smaller 
scale for every earlier Spectrum view ; but so arranging them one over the other, each with 
its own sized numerical graduation above it, that I trust there will be the least difficulty and 
the most satisfaction practically possible, in comparing details of the one with the other, and 
fixing the dates when real advances of observation — knowledge were made. 

C. P. S. 



Roy. Soc. Edin k 



Vol. XXXII. Plate XV. 



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( 45 ) 



IV. — Observations on the Annual and Monthly Growth of Wood in Deciduous 
and Evergreen Trees. By the late Sir Robert Christison, Bart., and 
Dr Christison. 

(Read 19th March 1883.) 

Having undertaken to continue the observations on the growth of trees 
commenced by my father in 1878, and carried on by him with unflagging zeal 
until a few months before his death in 1882, I give in the present paper the 
measurements made by him in 1881, which he did not live to publish, and those 
made in 1882 by myself. I shall also endeavour to point out the conclusions 
which may be drawn from the whole series of observations, beginning in 1878, 
arranging them under the heads of — 

I. Annual Observations. 
II. Monthly Observations. 
III. Influence of Weather on the Growth of Wood. 

Thus the deductions already arrived at by my father in this branch of his 
investigations on the growth and measurement of trees will be again reviewed 
and tested by the experience of two additional years. The other branches of 
his subject, including his inquiry as to the proper mode of measuring the girth 
of trees, the kind of information to be derived from such measurements, his 
discussion of Decandolle's rule for estimating the age of trees by the annual 
rings, the modes of doing so recommended by himself, and his description of 
the Fortingall Yew, have been so fully treated in his earlier papers, published 
in the Transactions of the Botanical Society of Edinburgh, as to require little 
further elucidation. Very different is it however with the yearly and monthly 
measurements. These can only become truly reliable after a prolonged series 
of observations ; and even the present review of five years' experience must be 
considered as to a considerable extent provisional and subject to correction. 

Before proceeding with the proper subject of this paper, it is advisable to 
state that the observations and deductions in it rest entirely on the possibility 
of making accurate measurements of the girth of trees. Previous to Sir 
Robert's observations measurements of the kind were made in the vaguest and 
most unreliable manner. It was reserved for him, in extreme but vigorous old 
age, to make the simple discovery that such measurements could be depended 
upon to within a tenth or even a twentieth of an inch, and that consequently 
not only the annual but even the monthly increase could be accurately recorded. 
I thought it was desirable however on taking up the subject as it dropped 
from his hands to retest this question, and to ascertain whether my measure- 
vol. xxxii. part i. h 



46 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 

ments might not, from some difference of manipulation, disagree with his. 
Accordingly, with the aid of my brother, I remeasured early in 1882 the forty- 
one trees in the Botanic Garden measured by Sir Robert at the end of the 
growing season in 1881. The result was satisfactory. In nineteen instances 
there was no appreciable difference between the two measurements ; in seven- 
teen the difference did not exceed a twentieth of an inch ; in three it 
amounted to a tenth, and in two to a seventh of an inch. Thus in only five 
cases were the discrepancies so great as to be of material consequence ; and, 
on investigation, these discrepancies were found to be evidently due either to 
extreme roughness or a tendency to scale in the bark. So great a degree of 
accuracy as this however cannot be obtained with ordinary tapes. I have found 
some of the inches marked on these a tenth of an inch too large, others a tenth 
too small. Another source of error with them is the terminal ring with the 
fastenings by which it is attached to the tape. If the measurement be taken over 
the ring, and it happens to be sunk in a depression of the tree, no error results ; 
but if the ring be on a projection of the bark, its bulk may cause an error in 
excess amounting to a twentieth or even a tenth of an inch. A different result 
from either of these will probably be got if the measurement is kept clear of 
the ring altogether. In the early part of his experiments Sir Robert used a 
tape, painted so as to avoid stretching, and graduated by himself; an extra 
inch graduated to tenths served for taking the fractions of an inch, so that it 
was unnecessary to graduate the tape throughout into tenths. But mistakes 
were apt to arise from the necessity of reckoning the tenths in a direction con- 
trary to the numbering of the inches, and ultimately he used a steel tape, 
graduated throughout to tenths, made specially for him by Messrs Chesterman. 
This is certainly the kind most to be recommended. 

I. Annual Observations. • 

Following Sir Robert's example, I give the increments for 1881 and 1882 
in a tabular form, along with those already published for previous years. As in 
the course of time however several of the trees originally selected have ceased 
to be eligible, I have found it necessary to remodel the table to a considerable 
extent. Thus the Scots fir, No. 19 in his list, and the Picea Lowei, 32, having 
ceased to grow, have been cut down; the Scots firs, 11, 36, 37, have also 
ceased to grow for three years ; and the yew, 47, is almost in the same predica- 
ment. As it was obviously useless to retain these, they have been struck out ; 
and the Pinus Laricio, 17, the aged sycamore, 13, and walnut, 14, having bark 
either so scaly or so rugged as to be unsuitable for minute measurements, have 
shared the same fate. In compensation for these losses in the Botanic Garden, 
a larger number of trees growing at Craigiehall, five miles from Edinburgh, have 
been selected for observation and added to the list. No confusion need be 
feared from these changes in making comparisons with former years, as the 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 



47 



increments are computed on the average increase per tree in the different 
classes. For the sake of clearness it has also been judged advisable to divide 
the table into two parts, the first comprising the twenty-eight deciduous and 
the second the twenty-three evergreen trees under observation. 

I have ascertained that the results obtained from this new list do not differ 
materially from those derived from the former list by Sir Eobert. But as it 
would be useless to cumber these pages with more than one set of observations, 
I have resolved to give the results of the new list alone, as being both more 
reliable when corrected so as to apply to the past, and forming a more accurate 
basis for the future. 



Table I. — Annual Increase in Girth of Deciduous Trees, 
All in the Botanic Garden or Arboretum, except tlvose marked " Craigiehall." 













Increase. 






Trees. 


Date and Girth 
when first measured. 




























1878. 


1879. 


1880. 


1881. 


1882. 






Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Birch, . 


1878 


55-35 


0-25 


0-05 


0-05 


o-io 


o-io 


„ (Craigiehall), 


1880 


56-30 






0-40 


0-55 


0-45 


Beech, , 


1878 


71-40 


1-20 


095 


0-65 


0-85 


1-15 


JJ • ■ • 


• )) 


60-50 


1-20 


0-80 


0-90 


0-90 


1-10 


,j . . . 


► )) 


75-80 


0-60 


0-60 


0-25 


0-50 


0-60 


>i 


• )> 


60-30 


0-60 


0-45 


0-15 


0-50 


0-50 


„ (Craigiehall), 


1880 


135-00 




• . . 


0-50 


0-65 


0-60 


>> >> • 


1878 


116-35 


6-80 


0-60 


040 


0-35 


0-65 


j, jj * 


' >> 


6175 


0-60 


0-30 


0-50 


0-50 


0-70 


>j jj 


■ J) 


71-85 


0-70 


0-50 


0-55 


0-65 


0-85 


Lime, . 


1878 


76-10 


0-50 


0-15 


o-oo 


0-65 


0-55 


j> • • 


» 


42-70 


0-70 


0-40 


015 


0-25 


0.40 


„ (Craigiehall), 


■ >) 


99-65 


0-20 


0-15 


o-io 


0-25 


0-35 


Sweet chestnut, . 


» 


70-80 


1-10 


0-90 


0-85 


1-10 


0-90 


Tulip tree, . 


» 


75-70 


1-00 


040 


0-30 


0-55 


0-50 


Horse chestnut, . 


i> 


48-75 


0-75 


0-50 


0-35 


0-70 


o-io 


Hawthorn, . 


)> 


38-00 


0-80 


o-io 


0-75 


0-35 


0-65 


Flowering ash, 


>) 


75-30 


0-60 


040 


0-30 


0-75 


0-50 


Sycamore, 


» 


58-60 


0-50 


0-20 


0-15 


0-30 


040 


English oak (Craigiehall 


)« 


69-45 


0-65 


0-50 


0-20 


0-35 


0-35 


Turkey oak, „ 


1880 


73-00 






0-70 


1-25 


0-90 


jj j; • 


1878 


41-90 


6-60 


0-65 


0-35 


0-60 


0-65 


American oak, 


yj 


30-80 


0-50 


0-40 


030 


0-30 


0-40 


Hungary oak, 


>> 


23-60 


1-80 


1-70 


1-40 


1-85 


1-85 


jj jj • 


1880 


1645 






1-10 


1-60 


1-90. 


jj jj • • 


J) 


13-50 






110 


1-70 


1-50 


Hornbeam, . 

Total increase of 22 tre 


1878 


44-50 


6-40 


0-35 


010 


0-55 


0-50 


es 














first marked in 1878, 






15-05 


11-05 


8-75 


12-90 


13-75 


Average per tree, 






0-68 


0-50 


0-40 


0-58 


0-62 


The same, with 5 addi 


3d 














in 1880, . 


. . . 




. • t 




12-55 


18-65 


19-10 


Average per tree, 


... 






... 


0-46 


0-69 


0-71 



48 



SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 



Table II. — Annual Increase in Girth of Evergreen Trees, 
All in the Botanic Garden or Arboretum, except those marked " Craigiehall." 













Increase. 






Trees. 


Date and Girth 














when first measured. 


















1878. 


1879. 


1880. 


1881. 


1882. 






Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Douglas pine, 


1878 


5610 


0-60 


045 


0-45 


0-60 


0-50 


>> >> 


» 


64-30 


0-80 


0-30 


0-35 


0-35 


0-40 


Pinus excelsa, 


t) 


30-90 


0-35 


0-20 


0-05 


0-30 


0-15 


» j> 


» 


32-70 


0-40 


0-20 


0-35 


0-35 


0-40 


Sequoia gigantea, . 


>> 


23-95 


1-15 


0-80 


1-00 


0-35 


0-70 


» » 


>> 


23-95 


1-75 


1-65 


1-80 


1-50 


1-40 


it j) 


■ J) 


18-95 


1-85 


1-50 


1-50 


1-30 


1-75 


» » 


M 


23-85 


1-25 


1-70 


1-55 


1-35 


1-65 


De9dar, 


a 


2610 


1-10 


0-70 


0-45 


0-35 


0-95 


» • 


>} 


64-00 


1-20 


0-60 


0-40 


0-25 


0-70 


Ticea Lowei, 


}> 


1500 


1-40 


1-25 


1-40 


0-90 


1-05 


Araucaria, . 


;, 


18-10 


0-60 


0-50 


0-55 


0-50 


0-45 


>» ■ ■ 


>} 


20-20 


0-50 


0-90 


0-75 


0-60 


0-85 


„ (Craigiehall), 


1879 


1790 




0-85 


0-65 


0-45 


0-70 


Atlas cedar, . 


1878 


27-55 


.1-65 


140 


1-75 


1-40 


1-60 


Evergreen oak, 


1879 


29-05 




0-40 


o-io 


o-io 


0-25 


Yew, . 


1878 


67-60 


6-60 


0-60 


0-35 


0-50 


0-50 


„ 


>? 


34-10 


0-50 


0-15 


0-20 


0-30 


0-45 


>/ » 


1879 


37-50 




0-60 


0-40 


0-40 


0-55 


,, • > 


» 


2350 




0-30 


0-35 


0-45 


0-55 


,, • • • 


• >> 


33-30 




0-45 


0-40 


0-35 


0-45 


„ f • ■ 


1880 


32-35 






0-15 


015 


0-40 


Cypress (Craigiehall), 
Total increase of 1C 


1879 


14-20 




0-80 


1-15 


0-85 


0-85 
















trees first measurec 


, 














in 1878, . 






15-70 


12-90 


12-90 


10-90 


13-50 


Average per tree 


. . . 




0-98 


0-80 


0-80 


0-68 


0-84 


The same, with 7 addec 
















in 1880, . 










16-10 


13-65 


17-23 


Average per tree 


. . * 








0-70 


0-59 


0-75 






The most remarkable result from the whole series of observations is the 
want of correspondence between the deciduous and evergreen classes in the 
increase and decrease of the growth of wood in the different years under review. 
Thus, as the tables show, a remarkable decline took place in both classes in 
1879 as compared with 1878, the average growth of each tree for these years 
in the deciduous class being 0*68 in. and 0'50 in., and in the evergreen class 
0-98 in. and 0*80 in. But in 1880, while the deciduous average declined still 
further, — to 040, the evergreens remained quite stationary ; * and in 1881, when 

* Sir lloiiF.m Christison believed that they also had declined, although to a less extent, but he was 
misled by an error in the figures of his MS. 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 49 

the deciduous average rose decidedly, — from 40 to 0*58, the evergreens 
suffered a decided fall, — from - 80 to 0'68. In 1882 the difference was not so 
remarkable, as the average of both rose, but in the case of the evergreens to 
much the greater extent of the two. 

I shall endeavour to explain the causes of these differences at the conclu- 
sion of this paper, under the head of the connection of weather with the growth 
of wood. 

Sir Robert Christison was inclined to attribute to the oak tribe a greater 
power of resisting inclement winters than other leaf-shedding trees possessed. 
At page 84, part iv. of his paper, he states that while leaf-shedding trees in general 
suffered a reduction of 41 per cent, in their increment in 1879 as compared with 
1878, seven oaks measured by him lost only 10 per cent. Unfortunately, for 
various reasons, all these oaks are not available for comparison in subsequent 
years, but at page 168, part v., he showed that the average increments of fifteen 
leaf-shedding trees in three successive years down to 1880 were 0"80 in., 0*45 in., 
and 0'35 in., and that the corresponding numbers for four of the oak tribe were 
0*82 in., 077 in., 0*54 in., a result still favourable to the oaks, although not so 
much so as in the previous instance. But if the facts be examined in detail, it 
is evident that this apparent superiority of the four members of the oak tribe is 
really due to one of their number — the hardy and quick-growing Hungary oak 
— and that the other three, although they suffered little loss in 1879, fell off 
greatly in 1880. It must be considered also that all these trees, with the 
exception of the hornbeam, which Sir Robert classed with the oaks, are of 
foreign origin. If we reckon the growth of the hornbeam with that of the only 
two British oaks whose measurements are at all reliable, the result is most 
disastrous for our native oaks ; for while their united growth in 1878 was 205 
in. and in 1879 1*65 in., it was only 0'70 in. in 1880. In these experiments 
the number of trees may be too small to give thoroughly reliable results, but it 
certainly seems probable that the foreigners — the Hungary, American, and 
Turkish oaks— stand severe winters, in our neighbourhood at least, better 
than our native oaks, the Hungary oak being much the hardiest of ail, 
while the British oak comes out worse than any other species of tree under 
observation. 

The yew seems to form an exception to the rule that the increment of wood 
in evergreen trees continued to decline in 1881, notwithstanding the remarkable 
rally made in the leaf-shedding class in that year. We have seen that the 
average growth of all the evergreen trees declined from 0*80 in. in 1880 to 0'68 
in 1881 ; but if we take the yews alone, five in number, we find that their 
average growth rose from 0*35 in. in 1880 to 0'40 in 1881. Thus in the wave 
of decline and rise during the three severe winters they followed the deciduous 
group, and not their relations the evergreen Pinacese. 



50 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 

II. Monthly Observations. 

* Encouraged by the results of his annual measurements, Sir Robert 
Christison selected in 1880 five deciduous and six evergreen trees, already- 
ascertained to be quick growers, as suitable for monthly observations. These 
trees comprised two beeches, three Hungary oaks, four Sequoias, one Araucaria, 
and an African cedar. They were measured at the end of May, June, July, 
August, and September. The operation was repeated by himself in the same 
months, with the exception of May, in 1881 ; and again by me in 1882, 
with the exception of August. Thus a tolerably complete record of the 
monthly increments of these trees was obtained for three seasons. As the 
number experimented upon, however, was both too limited and comprised too 
few species to give altogether reliable results, I commenced in 1882 to make 
monthly measurements of a considerably larger number, and henceforth twenty- 
eight- deciduous and eighteen evergreen trees, including twenty-two species, 
will be under observation. 

I shall now proceed to consider the conclusions to be derived from these 
measurements in the solution of the following questions : — 1, What are the 
months to which the groivth of wood is confined (a) in deciduous trees as a class 
and (b) in evergreens as a class ? 2. In which month is the groivth of wood 
most active in these two classes (a and b) respectively? 3. What are the 
peculiarities in these respects of different species of trees f 

In the Tables III., IV., and V. the facts will be found in detail on which 
the subsequent conclusions are founded. Table III. gives the three years' 
measurements and average growths of the smaller number of trees originally 
selected by Sir Robert ; Tables IV. and V. the results of a single year's observa- 
tions on the larger number, measured for the first time in 1882. The trees in 
this list only partially correspond with those used for annual observations, as a 
considerable number of the latter, from growing too slowly or from other causes, 
are not reliable for minute measurements. 

1, a. The Months to which the Growth of Wood is confined in Deciduous Trees. 

From the measurements made in 1880 on his five selected trees, Sir Robert 
came to the conclusion that the growth of wood in leaf-shedding trees is con- 
fined in general to the months of June, July, and August. I think however 
that he underrrated the importance of the May growth. It amounted to 12 per- 
cent, of the annual total, which it must be admitted is a substantial sum. It 
was due however almost entirely to the three Hungary oaks, the increase in 
the two beeches having been scarcely appreciable. Unfortunately the measure- 
ments for 1881 were not taken till the end of June, so they are not available 
for this inquiry. But after the unusually mild winter of 1882 the May growth 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 



51 



was nearly twice as great as in 1880, amounting to 21 per cent, of the annual 
increase. Again no doubt it was mainly due to the Hungary oaks, their pro- 
portionate growth for May having been 24 per cent, of their annual increase ; 
still the beeches were not idle, their corresponding growth amounting to 10 
per cent. And although the Hungary oak — exceptional among deciduous 



Table III. 



-Monthly Increase in Girth, in hundredths of an inch, of Five Deciduous 
and Six Evergreen Trees in the Botanic Garden. 





1880. 


1881. 


1882. 




May 

May. June, and 

June. 


July. 


Aug. 


Sept. 


May 

and 

June. 


July. 


Aug. 


Sept. 


May 
May. June and 
June. 


July. 


Aug. 
and 
Sept. 


Deciduous Trees — 






















Beech, . 


•00 + -25 = -25 


•50 


•10 


•00 


•20 


•25 


•35 


05 


•10 + -35 = -45 


•40 


•30 


» 


•10 + -30 = -40 


•20 


•35 


•05 


•35 


•35 


•15 


•05 


15 + -30 = -45 


•30 


•35 


Hungary oak, 


•30 + -40 = -70 


•40 


•30 


•00 


•60 


•50 


•65 


•05 


•30 + -45 = -75 


•60 


•50 




•05 + -40 = -45 


•30 


•30 


•05 


■65 


•45 


•50 


•00 


•35 + -50 = -85 


•55 


•50 


» » 
Total, . 


•20 + -30 = -50 


•30 


•25 


•05 


•60 


•55 


•50 


•00 


•65 + -15 = -80 


•50 


•20 


0-65 + l-65 = 2-30 


1-70 


1-30 


015 


2-40 


2-10 


2-15 


015 


1-55 + 1-753= -30 


2-35 


1-85 


Average per ) 
tree, . . J 


0-13 + 033 =0-46 


0-34 


0-26 


0-03 


0-48 


0-42 


0-43 


0-03 


0-31 + 0-35=0-66 


0-47 


0-37 


Monthly per- \ 
centage, . J 


12+ 30= 42 


31 


24 


3 


35 
•40 


31 


32 


2 
•00 


21+ 23= 44 


31 

•10 


25 
•05 


Evergreen Trees — 
Sequoia, 


•40+ -25= -65 


•40 


■05 


•00 


•00 


•15 


•25+ -30= -55 




•55+ -50 = 1-05 


•70 


•15 


•00 


1-00 


•05 


•45 


•00 


•45+ -65 = 1-10 


•20 


•10 


>> 


•70+ -40=1-10 


■30 


•00 


•00 


•85 


•25 


•20 


•00 


•75+ -65 = 1-40 


•25 


•10 


» • 


•55+ -40= -95 


•45 


•00 


•00 


•75 


•30 


•30 


•00 


•55+ -55 = 1-10 


•40 


•15 


Araucaria, 


•40+ -15= -55 


•15 


•05 


•00 


•35 


•10 


•15 


■00 


•45+ -10= -55 


•15 


•15 


Atlas cedar, . 
Total, . 


•45+ -30= -75 


•40 


. -50 


•05 


•55 


•35 


•50 


•00 


•35+ -40= -75 


•40 


•45 


3-05 + 2-00=5-05 


2-40 


0-75 


0-05 


3-90 


1-05 


1-75 


o-oo 


2-80 + 2"'65 = 5-45 


1-50 


1-00 


Average per \ 
tree, . . j 


0-51 + 033 = 0-64 


0-40 


0-12 


0-01 


0-48 


017 


0-29 


o-oo 


0-46 + 0-44=0-90 


0-25 


0-17 


Monthly per- \ 
centage, . j 


37+ 24= 61 


30 


9 





51 


18 


31 





35+ 33= 68 


19 


13 


trees for its 


early vigour — v 


mdn 


y ra 


ises 


the 


aver, 


xge 


in sc 


> small a numb 


er oj 


f 



trees in general. For if we include the whole of them, twenty-five in number, 
other than Hungary oaks, which were measured for the purposes of this inquiry 
for the first time in this same year, their average growth in May proves to be 12 
per cent, of the annual increase. Including the three Hungary oaks the pro- 
portion amounted to 16 per cent. 






52 



SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 



At the conclusion of the growing season the limit is probably more fixed. 
Neither in 1880 nor in 1881 was a greater increase than a twentieth of an inch 
recorded in any tree in September. So small an amount as this comes within 

Table IV. — Monthly Increase in Girth of Twenty-Eight Leaf-Shedding Trees in the 
Botanic Garden, Arboretum, and at Craigiehall in 1882. 







Increments 


in hundredths of an 


inch. 


No. 


Trees. 


Girth 31st 
March. 
























May. June. 


July. 


August. 


7 


Beech, ..... 


75-05 


•10 


35 


•40 


•30 


8 


• • • • 


64-30 


•15 


30 


•30 


•35 


14 


>j ■ ' 


77-85 


•05 


20 


•20 


•15 


38 


)> • * 


62-00 


•00 


15 


•30 


•05 


8 - 


Craigiehall, 


13615 


•00 




•25 


•15 


9 


j> » ... 


118-45 


•10 


15 


•25 


•15 


14 


a >» ... 


63-70 


•15 


10 


•25 


•20 


15 


jj a ... 


74-30 


•15 


20 


•30 


•20 


22 


j) >"> ... 


98-35 


•10 


10 


•20 


•05 


40 


Hungary oak, .... 


30-35 


•30 


45 


•60 


•50 


54 


>>>>••■ 


19-15 


•35 


50 


•55 


•50 


55 


>y ff f * • 


16-30 


•65 


•12 


•50 


•20 


44 


American oak, .... 


32-55 


•15 


•10 


•15 


•00 


43 


Turkish oak, .... 


44-20 


•10 


■15 


•30 


•15 


10 


„ „ Craigiehall, . 


74-95 


•20 


•20 


•30 


•20 


12 


English oak, .... 


7115 


■05 


•05 


•10 


•15 


33 


Hornbeam, .... 


45-90 


•15 


•15 


15 


•05 


28 


Sycamore, 


59-75 


•00 


•25 


•15 


•05 


58 


it * * 


63-50 


•00 


•05 


•05 


•00 


7 


„ Craigiehall, 


127-75 


•00 


•25 


•15 


•05 


18 


Lime, ..... 


44-20 


•05 


•15 


•20 


•00 


21 


„ Craigiehall, 


100-35 


•00 


•05 


•15 


•25 


3 


Ash, 


77-35 


•20 


•15 


•15 


•00 


6 


„ Craigiehall, 


141-40 


- -10 


15 


•05 


•05 


4 


Spanish chestnut, 


74-75 


•05 


•20 


•30 


•35 


9 


Horse chestnut, 


51-05 


•00 


•05 


•05 


•00 


6 


Tulip tree, .... 


78-15 


■00 


•05 


•20 


•25 


5 


Birch, Craigiehall, 


57-15 


•00 


•15 


•20 


•10 
•16 


Average of the 28 trees, 




•11 


•18 


•24 


„ 3 Hungary oaks, 


. . . 


•43 


•37 


•53 


•40 


„ 25 others, .... 




•07 


15 


■20 


•13 


„ 9 Beeches, .... 




•09 


•19 


•27 


•18 


• Monthly percentage of 28 trees, . 




16 


26 


35 


23 


„ „ '■'< Hungary oaks, 




25 


20 


31 


24 


„ 25 others, 




13 


27 


36 


24 


„ „ 9 Beeches, . 




12 


26 


37 


25 



the limit of probable error ; it may be doubted, therefore, whether any increase 
really took place in that month ; but as the differences between the records of 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 



53 



August and September, trifling though they were, all indicated an increase, it is 
probable that a slight and altogether immaterial growth did occur. Measure- 
ments kindly made for me by Mr Sadler in 1882 to test this question further 



Table V. — Monthly Increase in Girth of Eighteen Evergreen Trees in the Botanic 
Garden, Arboretum, and at Craigiehall in 1882. 









Increments in hundredths of an 


inch. 


No. 


Trees. 


Girth 31st 
March. 
























May. 


June. 


July. 


August. 






Inches. 










25 


Sequoia, 


27-55 


•25 


•30 


•10 


•05 


27 


t) ..... 


30-65 


•45 


•65 


•20 


•10 


1 


jj i . . • • 


25-10 


•75 


•65 


•25 


•10 


2 


,, . . . . . 


29-70 


•55 


•55 


•40 


•15 


29 


Deodar, 


28-70 


•10 


■20 


•30 


•35 


30 


,, ... ■ • 


66-45 


•00 


•20 


•30 


•20 


34 


Araucaria, . • 


20-25 


•25 


•10 


•05 


•05 


35 


j) . . • • . 


22-95 


•45 


•10 


•15 


•15 


4 


„ Craigiehall, 


19-85 


•25 


■25 


•10 


•10 


31 


Picea Lowei, .... 


19-95 


•45 


•20 


•20 


•20 


5 


Douglas pine, . 


58-20 


•15 


•25 


•10 


05 


2 


Austrian pine, Craigiehall, . 


21-55 


•65 


•40 


•20 


•30 


39 


African cedar . . . 


33-75 


•35 


•40 


•40 


•45 


1 


Cypress, Craigiehall, . 


17-00 


•35 


•25 


•20 


•05 


41 


Yew, 


69-65 


•10 


•15 


•10 


•15 


48 


M 


38-90 


•15 


•15 


•20 


•05 


49 


,, . ... 


24-60 


•20 


•10 


•15 


•10 


53 


,, ..... 


32-50 


•20 


•00 


•05 


•15 


Aver 


age of 18 trees, .... 




•31 


•27 


•19 


•15 




4 Sequoias, 


. . . 


•50 


•53 


•24 


•10 




3 Araucarias, . 




•31 


•15 


•10 


•10 




4 Yews, .... 




•16 


•10 


•12 


•11 




2 Deodars, 




•05 


•20 


•30 


•27 


Monl 


My percentage of 18 trees, . 




34 


29 


2-1 


16 




4 Sequoias, . 




36 


39 


28 


7 




3 Araucarias,. 




47 


23 


15 


15 




4 Yews, 


. . . 


33 


20 


25 


22 




2 Deodars, 




6 


24 


37 


35 



proved unfortunately unavailable, owing to inaccuracies in the tape used. But 
as the increment for August and September combined was less than in the two 
previous years, it is fair to conclude that there could have been no material 
growth in the latter month. 

1, b. The Months to which Growth of Wood is confined in Evergreen Trees. 

From the monthly measurements in 1880 of the six originally selected trees, 
Sir Robert concluded that the evergreen class begins to increase materially in girth 

VOL. XXXII. PART I. I 



54 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 

in May, a month earlier than leaf-shedding trees. This conclusion is amply con- 
tinued by the measurements of the two succeeding years. In 1881, indeed, the 
proof is not positive, as the first measurements did not take place till the end of 
June ; but as 51 per cent, of the whole annual growth was accomplished by that 
date, it is fair to conclude that a considerable proportion of the increase must 
have taken place in May. In 1882 there is no room for doubt. The increment 
till the end of that month actually exceeded the increment of any other month, 
and the only question is whether a portion of that remarkable growth was 
not due to April. Unfortunately, as no measurements were taken at the end of 
that month, this point must remain doubtful. 

But the reliability of results obtained from so limited a number of trees and 
species may justly be questioned. At all events, it may be held that, although 
true of these species, they may not be true of evergreens in general. Fortunately, 
however, these results are amply corroborated by observations on the larger 
number of evergreen trees, first measured for monthly comparison in 1882. 
The proportion of annual increment in these eighteen trees due to May was 34 
per cent., almost identical with that of the selected six, which was 35 per cent. 

The limit of the growing season in evergreen trees is better ascertained at 
the end than at the beginning. Of the six selected trees only one — the African 
cedar — showed the slightest trace of increase in September, and that only in 
one of the two years in which observations are available. The increment 
recorded, moreover, was so slight as to come within the limit of probable 
error. 

In August the proportionate growth seems to be much less in evergreen 
than in deciduous trees. In August 1880 the increment of the six selected 
evergreen trees was only 9 per cent, of the annual increase, while in the 
deciduous group it was 27 per cent. In 1881 there was a greater equality, the 
respective percentages being 31 and 34. But in 1882 that of the evergreens 
again fell to 13, while the deciduous percentage reached 25. The results for 
the latter year were confirmed by the observations on the larger number of 
eighteen evergreen trees, whose proportionate growth for August was only 15 
per cent, of the annual increase. 

On the whole, the conclusions to be drawn from all these observations are — 
First, that in ordinary seasons the growth of wood in deciduous trees is mainly 
confined to June, July, and August. In September it is scarcely appreciable. 
In May however a small growth does take place, which in favourable seasons 
may become of no insignificant amount. The Hungary oak not only grows 
with exceptional vigour in May, but probably in favourable seasons makes a 
start in April. Secondly, that evergreen trees as a class begin to grow probably 
a month earlier than the deciduous group. They make substantial progress 
in May, and some of them perhaps make a start in April. On the other 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 55 

hand, the measurements indicate that they stop growing somewhat earlier 
than the deciduous class. 

Thus Sir Robert Christison's conclusions are substantially confirmed, 
although the growth of deciduous wood in May is probably of somewhat 
greater importance than he supposed. It must be remembered, however, that 
these rules apply only to the neighbourhood of Edinburgh. In the milder 
climate, aided by a richer soil, of the south-western districts of Britain, where 
the leaves expand two or three weeks earlier than here, it is to be expected 
that the growth of wood will also be correspondingly earlier. Other leaf- 
shedding species besides the Hungary oak may also be found to be exceptional 
in the early vigour of their growth, as Sir Eobert's observations and my own 
include but a small proportion of the numerous native and foreign trees which 
thrive in our islands. 

A greater irregularity in the distribution of the monthly growth of the 
evergreens as compared with the deciduous trees occurred in all the three 
years during which monthly measurements were made. Thus, while the July 
percentages of growth in deciduous trees as shown in Table III., were 31, 31, 
and 31 in these three years, in the evergreen group they were 30, 18, and 19. In 
August the differences were still more striking, the respective figures being 
24, 32, 25 for the deciduous group, and 9, 31, 13 for the evergreen. 

It is remarkable that in 1881 the growth of the six evergreens, which in 
July amounted to only 18 per cent, of the annual increment, became vigorous 
again in August, when it reached 31 per cent. The deciduous group seemed 
to partake in this exceptionally vigorous growth in August 1881, but to a much 
less degree, the proportions being 31 per cent, for July and 34 per cent, for 
August. In treating of the influence of weather on the growth of wood I 
shall endeavour to explain these apparent anomalies. 



2, a. The Months in which the Growth of Wood is most active in Deciduous Trees. 
Table VI. — Monthly Percentages of Increase in Girth of Deciduous Trees. 





May 

May. June. and 

June. 


July. 


August 


Sept. 


5 Selected deciduous trees, 1880, . 

1881, . 

1882, . 

28 Deciduous trees, 1882, 


12 + 30 = 42 
35 

21 + 23 = 44 

16 + 26 = 42 


31 
31 
31 

35 


24 
32 
25 

23 


3 

2 



To elucidate this subject I give in Table VI. the percentage of growth due 
to each month of the years 1880, 1881, and 1882, in the five originally selected 



56 



SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 



deciduous trees, and the corresponding results for the growing months of 1882 
in the larger number of trees then under observation. 

The Table shows that in 1880 June and July were the best growing months 
for the five selected trees. The amount in these two months was nearly equal. 
The united growth of August and September, of which September's share was 
very trifling, was not much less than that of June or July, while that of May 
was only half that of August. 

The year 1881 is not fully available for this inquiry, no measurements 
having been taken for May ; but as the united growth of May and June but 
little exceeded that of July or August, it is fair to conclude that the increase in 
June alone was less than in either of the subsequent months. 

In 1882 the growth of the five trees in question was apparently distributed 
over a longer period. May takes a more prominent place with 21 per cent. 
The growth for June and combined August and September is not much 
greater, while July takes a decided lead with 31. The preponderance of the 
early-growing Hungary oak in the small number of selected trees, however, 
gives a false impression of the increased deciduous growth in May of this year. 
If we consider the whole number of deciduous trees, twenty-eight in all, under 
observation in 1882, the percentage for May is reduced to 16, which is still, 
no doubt, a substantial and probably an unusual amount. 



2, b. The Months in which the Growth of Wood is most active in Evergreen 
Trees. 

Table VII.— Monthly Percentage of Increase in Girth of Evergreen Trees. 





May. June. M T a ? and 
J June. 


July. 


August. 


6 Selected evergreen trees, 1880, 

„ „ 1881, 

1882, 

18 Evergreen trees, 1882, . 


37 + 24 = 61 

51 

35 + 33 = 68 

34 + 29 = 63 


30 
18 
19 

21 


9 
31 
13 

16 



It is more difficult to determine from the available data the month of 
greatest growth in evergreen than in deciduous trees. Not only are the varia- 
tions in this respect in different years greater in the former than the latter, but 
it is doubtful whether a part of the increment attributed to May ought not to 
be credited to April in the case of evergreen trees. This doubt arises from 
Sir Robert having concluded, probably too hastily, that no growth takes place 
in April. I can find no evidence in his papers of his having ascertained this by 
measurement, and I do not know how he came to form and act upon that con- 
clusion. Further observations are evidently necessary to settle this doubt, and 



. GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 57 

these I hope to undertake in future years.* At present all that we can safely 
say is that the increase of wood in evergreen trees from the beginning of 
spring till the end of May probably exceeds on an average that of every subse- 
quent month. Table VII. shows that it did so in the case of the six selected 
trees in 1880 and 1882, also in the eighteen trees measured in the latter year. 
In 1881 the observations are incomplete, as separate measurements were not 
made for May and June, but August — with 31 per cent. — has a strong claim 
to the highest place, due I believe to exceptional circumstances. 

One of the most remarkable conclusions that may be drawn from the three 
years' monthly observations on evergreen trees, as a class, is that they appa- 
rently accomplish the greater part, and sometimes much the greater part, of 
their growth by the end of June. Thus in 1880, 64 per cent., in 1881, 51 per 
cent., and in 1882, 68 per cent, of the annual increment of the six selected trees 
was finished by that date, and the increment of the eighteen trees measured in 
1882 was almost identical with that of the six in the same period, amounting to 
63 per cent. Apparently then it is not heat alone which regulates the growth of 
wood in many evergreen trees. By some inherent vital power they complete the 
greater part of their growth before the commencement of the two warmest 
months in the four which constitute the growing period, or else their vital power 
is so exhausted in the early part of the season that growth cannot be carried on 
with vigour when the real heat of summer comes on. 

In conclusion, it must be allowed'that further observations, both on deciduous 
and evergreen trees, are required to determine which is the best growing month 
in each class. At present the indications are in favour of July for the former 
and May for the latter, if the whole, or nearly the whole, of the growth hitherto 
ascribed to that month really belongs to it.* 

3. Monthly Increase in certain Species of Trees. 

There is considerable variety in the vigour of growth in different species 
both of deciduous and evergreen trees in the different months of the growing 
season. My observations on this point indeed, on any considerable number of 
trees, extend only to a single year, but the results are sufficiently striking to 
deserve attention. In Table VIII. are given the percentages of monthly growth 
in seven species, which, either from the number of specimens under observation, 
or from the certainty of their measurement, yield the most reliable results. 

The Hungary oak begins to grow earlier than any other of the deciduous 
trees under observation. In the backward spring of 1880 the three specimens 
marked in the Botanic Garden were well clothed with foliage on the 15th May, 

* Since this paper was read, the spring measurements for 1883 show a growth in April amounting 
to two-fifths of that in May in twenty evergreens under observation. It appears probable therefore that 
June is the month of greatest growth for evergreens. 



58 



SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 



and after the wonderfully mild winter of 1882 one of them was beginning to 
expand its leaves on the 27th of March. Their growth was more evenly dis- 
tributed over the four growing months than that of any others of the deciduous 
group, and among the evergreens the yews alone rivalled it in that respect. 
The Turkish and American oaks seem also to be early growers. The propor- 
tion of their May growth was not much less than that of the Hungary oaks, 
still in both the first and last months of the growing season they were less active 
than the latter. The British oak grows poorly in this district, and besides, 
from the roughness of its bark, it is not suitable for minute measurements. 
The only one experimented upon showed no appreciable increment in May. 

The beeches made only 12 per cent, of their annual increment in May, about 
half the proportion of the foreign oaks, and as this was in an unusually early 
season it is probable that in ordinary years their May growth must be very trifling. 

Table VIII.— Monthly Percentage of Increase in Girth of Seven Species of 

Trees in 1882. 





Till 31st 
May. 


June. 


July. 


August. 


3 Hungary oaks, .... 


25 


21 


31 


23 


2 Turkish and 1 American oak, . 


22 


22 


38 


18 


9 Beeches, ...... 


12 


26 


37 


25 


4 Sequoias, ..... 


3G 


39 


18 


7 


3 Araucarias, ..... 


48 


22 


15 


15 


2 Deodars, 


6 


24 


37 


33 


4 Yews, 


33 


20 


25 


22 



Among other deciduous species, which being less reliable do not find a 
place in this Table, the ash and the hornbeam alone showed an appreciable 
growth in May. It is fair to state however, that in the Edinburgh district the 
horse chestnut leaves were almost universally destroyed in 1882 by early frost 
and the ravages of insects. It is no wonder therefore that the specimen 
measured in the Botanic Garden grew only a tenth of an inch in the year. 

The Sequoias were remarkable, even among evergreens, for the early vigour 
of their growth. No less than 75 per cent, of their annual growth was finished 
by the end of June. But they ceased to increase earlier than any of the other 
species, their growth in August being only 7 per cent. 

The Araucarias also grew rapidly in the early part of the season, accomplish- 
ing very nearly one half of their annual increment by the end of May, and 70 
per cent, by the end of June. 

With the Deodars it was exactly the reverse, 70 per cent, of their increment 
taking place after June. If the observations for a single year on two trees may 
be trusted, the Deodar is an exception to the general rule of early growth in 
evergreens 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 



59 



The increase of the yews was nearly equally divided between the first and 
second periods of the season. The former had indeed a slight advantage, but 
the spring of 1882 was unusually early, and a longer experience may show 
that yews do not follow the rule of early growth which appears to hold 
good in most of the Pinacese. 

As it may be of some interest to show the comparative rate of growth of 
wood in certain species of trees under observation, I give the following Table : — 

Table IX. — Average Increase in Girth of Eight Species of Trees for Three Years. 





1880. 


1881. 


1882. 


Average. 


Average of — 


Inch. 


Inch. 


Inch. 


Inch. 


3 Hungary oaks, 


1-20 


172 


1-75 


1-55 


1 American and 2 Turkish oaks, . 


0-45 


0-75 


0-65 


0-62 


9 Beeches, ..... 


0-53 


0-64 


0-79 


0-65 


4 Sequoias, ..... 


1-46 


117 


1-40 


1-01 


3 Araucarias, .... 


0-65 


0-51 


0-66 


0-61 


2 Deodars, 


0-42 


0-30 


0-82 


0-51 


4 Yews, ..... 


0-31 


0-37 


0-50 


0-39 


1 African cedar, .... 


1-75 


1-40 


1-60 


1-58 



III. Influence of Weather on the Growth of Wood. 

This is a complicated inquiry, so many and various are the influences which 
may come into play. Extreme frost, prolonged frost, the amount of heat and 
sunshine, drought or excessive rain, strong winds, all no doubt affect the 
growth of wood, their influence varying with the seasons, and not necessarily 
showing their effects immediately. 

Of all these agents cold is probably the most energetic ; I have there- 
fore looked to it mainly for explanation of the differences in annual growth, 
adopting Mr Sadler's record of temperature in the Botanic Garden as my 
guide, because the greater number of the measured trees are situated either 
there or in the adjoining Arboretum. The thermometers used by him are four 
feet from the ground, and being unprotected the readings are not strictly 
accurate, but for purposes of comparison with each other the observations are 
sufficient. 

Sir Robert Christison showed that the remarkable cold and absence of 
sunshine in the spring and summer of 1879 caused a great deficiency in the 
growth of wood, both in deciduous and evergreen trees, in that year as com- 
pared with the previous one ; that the deficiency was greatest in the deciduous 
class ; and least of all, so far as his observations went, in oaks. 

In 1880 the spring was favourable to the opening buds, the temperature 



60 SIR ROBERT CHRISTISON AND PR CHRISTISON ON THE 

being considerably above average in February and March, while although 
April was cool it was free from severe frosts. The summer was also of an 
average character. The foliage was therefore, in general, rich and abundant. 
Nevertheless there was again a great falling off in the growth of deciduous 
wood. This Sir Robert attributed to the extraordinary low temperatures of 
the previous December, succeeding an autumn unfavourable to the ripening of 
wood and formation of buds. He believed that evergreen trees had also 
suffered, although not to the same extent ; but I find that he had been deceived 
by an error in copying his figures, and that their growth in 1880 was almost 
identical with that of 1879. 

It is not easy to explain why both classes should have suffered a diminution 
in the growth of wood in 1879, and only the deciduous class a further decline 
in 1880. In the first of these years the cause of deficiency was no doubt, as 
Sir Robert believed, the inclement spring and summer, as the cold of the 
previous winter although prolonged was not remarkably intense ; under these 
circumstances both classes of trees were unfavourably influenced. In 1880 
on the other hand the cold of the previous winter was both prolonged and 
intense, and in all parts of the country its effects were visible in the killing 
of tender young wood or even of whole trees. It is no wonder then that 
the deciduous trees showed a marked decline in addition to the serious loss 
they had suffered in the previous year. But why did the evergreen class 
escape this further loss ? Possibly the explanation of this difference may 
be found in the earlier activity of growth in evergreens in spring. In their 
exposure to the intense frost of winter their circumstances must have 
been much the same as those of the deciduous class, but their compara- 
tively early buds would probably come under the influence of the genial March 
and April to a greater degree than the later buds of the leaf-shedding trees, 
which, on the other hand, would encounter a rather inclement May. Another 
cause that may be suggested is that the previous autumn, which was highly 
unfavourable to the ripening of wood, may have in some way prejudiced the 
evergreens less than the deciduous trees. That the evergreen trees under 
observation were not really hardier than the deciduous ones was proved by 
their fate in the following year. 

The winter of 1880-81 was even more protracted and severe than that of 
1879-80. Both the lowness of the average temperature and the number of 
extremely low readings at the Botanic Garden in January, the coldest month of 
1880-81, were more remarkable than in December, the coldest month of the pre- 
vious winter. Thus the lowest temperatures recorded in the latter month were 
1°, 4°, 15°, 17°, 19°, but those of January 1881 were 0°, 4°, 7°, 10°, 11°, 12°, 12°, 12°, 
13°, 14°. And this greater cold was prolonged far into the spring. On the last 
day of February and first few days of March 15°, 15°, 18°, and 19° were recorded, 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 61 

and another wave of cold brought the thermometer below the freezing point on 
twelve nights in the first fortnight of April, the lowest readings being 21°, 22°, 
and 23°. On the other hand, the lowest readings in the same months of 1880 
were only 23° in February, 22° in March, and 27° in April. Moreover, the total 
number of nights of frost in these three months in 1880 was only thirty-four, 
while in the corresponding period of 1881 it was fifty-three. 

After so severe a winter and spring it might have been expected that even 
more disastrous effects on the growth of wood would have resulted than after 
the less extreme cold of the previous year. But, on the contrary, the deciduous 
trees, at least, made a remarkable rally, the average growth of twenty-seven 
of them having risen from 0'46 in. in 1880 to 0'69 in. in 1881, an increase of 
nearly one-third. Very different however was the fate of the evergreen trees. 
Unlike the deciduous class they had successfully resisted the efforts of the 
previous hard winter, but now they suffered seriously, thus differing once more 
from the leaf-shedding trees, but in the opposite way, for their average growth, 
which in 1880 had been 070 in., was now only 0*59 in. 

The wonderful rally made by the leaf-shedding trees in 1881, notwithstanding 
the almost unprecedentedly low temperatures of the previous winter, can only be 
accounted for, I believe, by the favourable character of the preceding autumn, 
which allowed the growth of wood of 1880 to be perfectly matured, and so enabled 
it to withstand the rigour of the winter in 1881. But why was a similar effect 
not produced upon the evergreens ? Is it because the maturing of wood is not 
so effectual with them as it appears to be with the deciduous trees in enabling 
them to resist a severe winter 1 Or shall we find the reason in the compara- 
tively early growth of evergreens which might expose their tender buds to the 
frequent low temperatures of March and April, a danger from which the buds 
of the deciduous class, coming out later, would be free, while they would benefit 
by the geniality of May ? The latter seems the most probable cause, but 
further observations are required to settle the question. 

The winter of 1881-82 was one of the mildest on record. It was well 
suited therefore to test Sir Robert's suggestion that evergreens might in an 
unusually mild winter show some trace of growth ; but none could be detected 
in any of the twenty-eight measured trees. Vegetation however was very 
early. A sycamore and a Hungary oak among the marked trees in the Botanic 
Garden began to expand their leaves on the 27th of March. The sycamore 
paid dearly for its temerity. Caught by an early frost and afterwards attacked 
by insects, its leaves were irretrievably injured, and its increase in girth for the 
year only amounted to a twentieth of an inch. A similar fate befell nearly all 
the horse chestnuts near Edinburgh, including a fine specimen, one of my 
measured trees, which grew only a tenth of an inch in the year. The Hungary 
oak, on the other hand, did not suffer at all. The deciduous class as a whole, 

VOL. XXXII. PART I. K 



fr> SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 

however, were not injured in this way ; but notwithstanding the mild winter they 
only maintained their . improvement of the previous year, without attaining the 
standard of growth of 1878. The reason of this failure, no doubt, was the 
unfavourable nature of the previous autumn for the ripening of wood, combined 
with the ungenial nature of the growing season, both of which were well-marked 
evils at the Botanic Garden, as I was informed by the late lamented Mr Sadler 
shortly before his death. 

The evergreens, on the other hand, recovered their loss of the previous 
year. Apparently the frost of April had not injured them, and they had been 
stimulated by the mildness of May, as their growth till the end of that month 
bore a high proportion to the whole annual increase. 

This attempt to connect the annual variations in the increase of wood with 
temperature, and to explain the curious contrasts between deciduous and 
evergreen trees in their annual growth by the effects of temperature alone, 
cannot' be considered as altogether satisfactory. Neither are the difficulties 
cleared up by considering other causes which must manifestly affect the 
growth of wood. Violent winds, for example, must be prejudicial not only by 
tearing down important branches, but by damaging the leaves. Every one 
must have observed the injury done to foliage by storms, particularly in spring 
and the beginning of summer. Multitudes of leaves are blown away, and 
those which remain hang limp and shrivelled from the branches, their petioles 
twisted by the wind, and the circulation through them thus hindered by bruis- 
ing of the vessels. In the records of the Scottish Meteorological Society many 
gales are reported as having occurred at Edinburgh in the years with which 
we have to do, but I cannot clearly trace a connection between them and any 
diminution in the growth of wood. I should have expected the greatest 
damage to have been done in 1881. In the previous year, indeed, there were 
three gales in May, but it was a backward spring, and the leaves may thus 
have escaped. At all events we know that Sir Robert remarked the richness 
and abundance of foliage in June, and there were no gales in that or the sub- 
sequent growing months. In 1881, on the other hand, one gale in May, three 
in June, two in July, and four in August were recorded ; yet this was the year 
in which, with all the disadvantage of a previous winter of almost unprece- 
dented severity, the growth of deciduous wood made a remarkable rally. But 
the fact is that the effects of each gale must be watched in order to know 
whether any general damage has been done to the leaves or not, so much 
depends on the strength of the wind, its direction, and the shelter which may 
protect the trees concerned. I should expect that differences between the 
annual increase of deciduous and evergreen trees might sometimes be due to 
this cause, as the leaves of the latter, from their shape, cannot be exposed to 



GKOWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 



63 



the same injury as those of the former ; but in the years now under considera- 
tion I cannot trace any such effect. 

In a climate such as ours, with frequent variations from the average in the 
monthly rainfall, considerable effects on the growth of wood may be expected 
from excess or deficiency of rain at the growing season. To trace these effects 
may be difficult, from the possible simultaneous action of other causes immediate 
or remote ; nevertheless I think something may be made of an examination of 
the principal abnormalities in the rainfall during the three years in which 
monthly observations of growth were taken. I owe to the kindness of Mr 
Buchan the following Table, showing the excess or deficiency of rain during the 
months of the period in question. The means from which these are calculated 
are derived from twenty-eight years' observations at Charlotte Square, whereas 
the monthly rainfall is taken from observations at Cumin Place, Grange ; but 
the general results are not likely to be seriously affected by this difference. 



Table X. — Monthly Excess or Defect of Rain at Edinburgh in 1880, 1881, and 1882. 





Jan. 


Feb. 


March. 


April. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


1880, . 

1881, . 

1882, . 


-1-69 

-0-70 
-0-55 


+ 0-03 
+ 2-81 
+ 0-01 


-0-09 
+ 0-13 
+ 1-04 


+ 0-11 
-0-32 
+ 1-00 


-1-05 

-0-04 
+ 0-29 


-0-46 
-0-61 
+ 0-28 


+ 1-91 
+ 0-52 
-0-51 


-2-46 
+ 3-06 
-0-85 


+ 0-17 
+ 0-97 


+ 1-66 
-0-50 


+ 1-54 
+ 0-60 


+ 1-01 
-0-83 



In comparing the rainfall with the tree-growth, I shall make use of the 
proportion which the monthly percentage of the latter bears to the whole annual 
growth. These will be found in Table VI. and VII. 

1880. — The rainfall of May was less than half the average, and that of June 
was deficient by about a third ; but the increase of wood in both classes of trees 
was quite up to the average of the same period for three years. In July the 
rainfall was much in excess : the deciduous growth was an average one ; but 
the evergreen growth was much above the average. In August there was a 
great deficiency of rain, — 2"46, and an excess of heat, + 3°*3 ; the deciduous 
growth was about an average, the evergreen greatly below average. 

1881. — In April, May, and June there was a deficiency of rain, but it only 
amounted to an inch in all, and as vegetation was completely checked by severe 
weather till the middle of April, the small proportionate growth of both classes 
of trees in May and June may fairly be attributed to the latter cause. In July 
the rainfall was slightly in excess : the deciduous growth was again an average, 
but the evergreen under average. In August, the memorable month of the 
Volunteer Review at Holyrood Park, no less than 6 inches of rain, double the 



64 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 

average, fell at Edinburgh : then the evergreens made a surprising rush, no 
less than 31 per cent, of their annual growth taking place, whereas in August 
1880 the portion was only 9 per cent., and in 1882, 13 per cent. This result 
was the more remarkable, as the temperature of the month was 2° "3 below the 
average. The deciduous trees were also apparently benefited by this excessive 
rain, although accompanied by deficient temperature, their proportion being 34 
per cent, in August and September of 1881, while it was only 27 per cent, in 
1880, and 25 per cent, in 1882. 

1882. — The rainfall of March, April, May and June was abundant, exceeding 
the average by an inch in each of the first two months, and being rather above 
the average in the third and fourth. In the same period the growth of ever- 
green wood was large, but this may easily be accounted for by the mild winter 
and early spring, without calling in the aid of the rainfall. 

Taking a general view of this investigation, it appears as if an abundant 
rainfall were favourable to the growth of wood, but much more favourable to 
the evergreen than the deciduous class. It must be admitted however that a 
longer series of observations, taken on a larger scale, are necessary to determine 
this point. The most striking fact shown is the extraordinary increased growth 
of the evergreens in August 1882, along with a very heavy rainfall and low 
temperature, whereas in the previous August, when the conditions were 
reversed, the rainfall being 2*46 inches in default and the temperature 3 0, 3 in 
excess, the evergreen growth was very deficient. 

Summary. 

To give a better idea of the general scope of this paper, the details of which 
are necessarily of a somewhat dry and tedious character, I now give a summary 
of the chief conclusions which are scattered throughout the text. It must be 
remembered however that these conclusions are strictly applicable only in the 
Edinburgh district, and that some of them are only indications of the probable 
truth, and require to be confirmed by a larger series of observations. 

1. The effects upon the growth of wood of the severe winters preceding the 
growing seasons of 1879, 1880, 1881 were not the same in deciduous and ever- 
green trees. In 1879 both suffered : the former more than the latter. In 
1880 a further decline took place in the deciduous class, but not in the other. 
In 1881 the deciduous class recovered their loss of the previous year, but it was 
now the evergreen's turn to fall off. After the unprecedentedly mild winter of 
1882 they again differed. For while the deciduous trees made no further 
recovery, the evergreens regained the loss sustained in 1881 ; neither class 
however attaining to the standard of growth in the favourable season of 1878. 

2. Evergreen trees probably do not increase their wood at all in winter, 



GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 65 

however mild it may be, as not the slightest trace of growth could be detected 
in the measured trees after the wonderfully mild winter of 1882. 

3. The British oak probably suffered a greater decline in its growth of 
wood from the severe winters than any other tree under observation. The 
Hungary oak, on the other hand, was less affected than- any other tree ; and 
the Turkish and American oaks less than our native oak. 

4. In the wave of increase and decrease in wood growth through these 
years the yews followed the deciduous class, and not their congeners the ever- 
green pines. 

5. The appreciable growth of wood in deciduous trees is mainly confined to 
June, July, and August in ordinary seasons ; but a material increase does take 
place in May, particularly when the spring is unusually mild. 

6. The growing season in evergreen trees includes May, and probably an 
appreciable start is made even in April, when the spring is favourable. 

7. The proportionate monthly growth seems to vary more in evergreens 
than in deciduous trees. 

8. The growth of wood is probably greatest in July in deciduous trees, and 
in June* in evergreens ; but further observations are required to settle these 
points. 

9. On an average of three years the evergreen trees as a class accomplished 
60 per cent, of their annual increase of wood before the end of June, the deciduous 
60 per cent, of theirs after that date. Deodars appear to be exceptional, as 
they agreed with the latter instead of the former group. In yews the growth is 
probably pretty equally divided between the two periods. 

10. Of all the species measured, the Hungary oak and African cedar proved 
much the quickest growers. Then followed the Sequoia gigantea. 

11. Thorough ripening of wood in autumn seems to be of immense con- 
sequence in enabling deciduous trees to stand extremely low temperature in 
winter. Evergreens however do not seem to be so dependent on it. 

12. An excessive rainfall seems to be favourable to the increase of wood, 
particularly in evergreen trees. A great excess of rain in August 1881 appar- 
ently stimulated the growth of wood in these to a remarkable degree, although 
the temperature of the month was decidedly low. 

In conclusion, I cannot help expressing a wish that others who have better 
opportunities than I can command would take up a line of inquiry which Sir 
Robert Christison has made easy by the practical rules he has laid down for 
its prosecution. The necessary observations are not difficult to make, merely 
requiring precision ; and they take up little time when the trees experimented 
upon are near at hand. The work is interesting, and the results may prove to 

* See foot note, page 57. 
VOL. XXXII. PART I. L 



66 GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 

be of importance in unexpected ways. I must also repeat the surprise which 
Sir Robert often expressed, that little or nothing seems to have been done to 
ascertain the effects of manuring on tree growth. " Mulches " have indeed 
been applied to favourite trees when in a sickly state, and often with the best 
results, but the farther step of trying the effect of manures in stimulating the 
growth of healthy trees has not, so far as I am aware, been taken. Perhaps 
the want of any reliable method of ascertaining the rate of growth of wood has 
hitherto stood in the way of such experiments ; but surely there is the greatest 
encouragement to undertake them, now that Sir Robert has shown the ease 
and accuracy with which minute measurements of the girth of trees can be 
made, and their rate of growth thus ascertained in comparatively short periods 
of time. If such application of manures proved useful, but at the same time 
too expensive to be employed on the great scale, it should at least be welcomed 
by the .landed proprietor to secure a more rapid growth of young ornamental 
wood. 



Note. — In Table III. the average growth of the Evergreen trees for May and June 1881 
should be 065 instead of 0'48, and the monthly percentages 59, 15, 26, instead of 51, 18, 31. 
The latter errors occur also in Table VII. The conclusions in the text are not materially 
affected by these errors, except that the claim of August to the highest average monthly growth 
in 1881, mentioned on page 57, becomes very doubtful. 



( 67 ) 



V. — A Contribution to the Chemistry of Nitroglycerine. By Matthew 
Hay, M.D., Assistant to the Professor of Materia Medica in the 
University of Edinburgh. 

(Communicated by Professor Crum Brown.) 

Introductory. — In the course of an inquiry into the physiological and 
therapeutical action of alkaline nitrites, and allied substances, I was struck 
with the strong resemblance which the action of nitroglycerine bears to that 
of the nitrites.* The resemblance is, indeed, so well marked, that the action of 
the one may be held to be identical with that of the other, unless in respect of 
intensity. The suggestion, therefore, naturally occurred to me, that nitro- 
glycerine is not a nitrate of glyceryl, as it is always represented, but a nitrite. 
For no ordinary nitrate, as an alkaline nitrate or nitrate of ethyl, nor any 
compound of glyceryl with another acid, as sulphuric acid, produces an action 
on the body at all resembling that of nitroglycerine. On referring to the 
various investigations which had been made for the purpose of ascertaining the 
chemical constitution of nitroglycerine, I found that none of them was 
sufficiently extended and exact to place beyond doubt its precise nature. The 
danger in manipulating so explosive a body had evidently prevented the 
various chemists from making a thorough examination of its composition. I 
at first thought that nitroglycerine might be a nitrite of glyceryl, having its 
nitrous acid so intimately combined with the glyceryl, that the acid did not 
exhibit its reactions when tested for in the usual way ; just as the acids of other 
ethereal compounds will not yield their usual reactions, unless special means 
are taken to forcibly dissociate the acid from the base ; for example, the acid 
of acetate of ethyl, or of chloride of ethyl. Certainly nitroglycerine gives no 
blue colour with a solution of starch and iodide of potassium and sulphuric 
acid, a. very delicate test for the presence of nitrous acid. In order, however, 
to apply the test to the separated acid of nitroglycerine, I mixed an alcoholic 
solution of nitroglycerine with an alcoholic solution of pure caustic potash. The 
potash was ascertained to be free from nitrite, which I have frequently found 
present in small quantity in various specimens of ordinary potash. Decomposi- 
tion of the nitroglycerine quickly occurred, and the fluid, when now tested for 
nitrous acid, was found to contain the acid in abundance, and so much of it, 
that for the moment I believed that nitroglycerine was, in reality, a nitrite of 

* Matthew Hay, Practitioner, March and June 1883. 
VOL. XXXII. PART I. M 



68 DR MATTHEW KAY ON THE 

glyceryl ; and hence the nature of its physiological action. Some estimations, 
however, of the quantity of the nitrous acid proved to me that whilst the larger 
portion of the nitrogen of the nitroglycerine appeared as nitrous acid in the 
decomposed products, yet a considerable portion was present in some other 
form. 

The production of a large amount of an alkaline nitrite, when nitroglycerine 
is decomposed by an alkali, is a fact which, very strangely, has hitherto 
escaped the observation of chemists. Muller and De la Rue * have, indeed, 
remarked the formation of nitrous acid in the spontaneous decomposition of 
badly-washed nitroglycerine ; and Hess and Schwab t have even stated that 
nitrite of potassium is formed in addition to nitrate of potassium when potash 
is allowed to act on nitroglycerine, but they appear to have believed that the 
nitrite was formed in small quantity, and was quite a subsidiary product of the 
decomposition. Ever since Railton,J in 1855, published his paper on " Nitro- 
glycerine and its Products of Decomposition by Caustic Potash," the 
decomposition has been invariably represented, and even in the most recent 
works on chemistry, by the equation: — C 3 H 5 .3^0.N0 2 ) + 3HKOH=:C3H 5 
.30H + 3(KO.N0 3 ) ; that is, caustic potash decomposes nitroglycerine with 
the formation of glycerine and nitrate of potash ; and it is mainly from the 
supposed correctness of this equation that the formula for the constitution of 
nitroglycerine has been derived. Williamson,^ in the following 3 r ear, gives 
an account of an investigation of nitroglycerine, and with results so exactly 
similar, even in detail, to those of Railton, that it is apparent that these 
chemists had made the investigation conjointly, although they published their 
results separately. Railton supplies a more minute account of his method of 
analysis of the products of decomposition, and it is not difficult to understand, 
from a careful perusal of it, how he was led to suppose that the nitrate of 
potash, which he obtained by crystallisation, was the only salt present. He 
applied no tests for nitrous acid, and he made no quantitative estimation 
either of the nitrate of potash or of the glycerine ; and I may anticipate some 
of the results of the present investigation, and say that it is highly improbable 
that he obtained any glycerine at all, as he probably mistook for glycerine a 
syrupy residue consisting of other substances. No succeeding investigator of 
the chemistry of nitroglycerine has examined much more minutely the decom- 
position products ; and the equation, therefore, remains as yet unaltered. It is 
evident that the constitution of nitroglycerine and the action of alkalies on 
nitroglycerine afford room for further investigation. 

* Muller und De la Rue, Liebicfs Annalen. d. Gkewie., CIX. 122. 

f Hesh und Schwab, Berichte d. deutsch. chem. GesdUchft. Bd. XT. (1878), S. 192. ' 

\ Railton, Qu. Journ. of Chem. Soc, vol. vii. p. 222. 

§ "Williamson, Pro'-. Roy. Soc. Lond., vol. vii. p. 130. 



CHEMISTRY OF NITROGLYCERINE. 69 

Action of Fixed Alkalies on Nitroglycerine. — The nitroglycerine used was 
made by myself and not extracted from dynamite, as has been very frequently 
the case with previous investigators. I shall afterwards describe the mode of 
preparation employed. It is sufficient in the meantime to state, that whatever 
was the variation practised in the method of the production of the nitro- 
glycerine, the products were perfectly uniform in character. The action of the 
alkali was examined both in aqueous and in alcoholic solutions. Nitro- 
glycerine is so insoluble in water that it was decidedly preferable to make use 
of an alcoholic solution of the ether and mix it with an alcoholic solution of 
pure caustic potash (crystallised from its solution in alcohol). Absolute ethylic 
alcohol was employed in every instance. 

When a moderately strong solution of caustic potash (1 in 10) is added to 
a solution of nitroglycerine of similar strength, the following phenomena are 
observed. The first few drops of the alkaline solution produce an orange- 
coloured precipitate, which, on the addition of more of the potash, assumes 
along with the whole fluid a deep reddish-brown colour. A large amount of 
heat is developed during the mixture, amounting almost to ebullition of the 
alcohol ; a strong aldehyde-like odour is evolved, without any perceptible 
odour of ammonia or acrolein. The fluid quickly separates into two layers — 
the lower, and much the smaller, being partly of the nature of a solid 
precipitate, yet in great part syrupy and of a very deep reddish-brown colour, 
and containing nearly all the colouring matter formed by the decomposition of 
the nitroglycerine. The upper layer constitutes the bulk of the fluid, and is 
yellowish in colour, and at first muddy, but, after a few minutes, becomes quite 
transparent. The application of external heat is, as I have ascertained, quite 
unnecessary to complete the decomposition, although in most of my 
experiments I have with this object boiled the fluid over the water-bath 
for several minutes, sometimes to the entire dissipation of the alcohol, water 
being added as the alcohol is evaporated. When water is so added, the syrupy 
precipitate, in proportion to the amount of alcohol still present, becomes 
partially or completely dissolved, yielding a deep reddish-brown solution. If 
sufficient water is added to the fluid without previous removal of the alcohol, 
it is still possible to obtain a perfect solution of all the substances present. It 
was in such diluted solutions, obtained either in the one way or the other, that 
I estimated the amount of nitrite of potassium formed. This was effected by 
means of starch, potassium iodide, and dilute sulphuric acid, a thoroughly 
well-boiled 5 per cent, solution of starch, and containing 2 per cent, of 
potassium iodide, being employed. The blue colour obtained on the addition 
of these reagents was compared, as regards its intensity, with the colour 
produced by a similar amount of the reagents added to standard solutions of 
nitrite of sodium placed in test-tube's of the same diameter and used in the 



70 DR MATTHEW HAY ON THE 

same quantity as in the case of the nitroglycerine solution. The purity of the 
nitrite of sodium was previously ascertained by titration with a standard 
solution of permanganate of potash ; and the strengths employed of the 
standard solutions of the nitrite were 1 in 500,000, and 1 in 1,000,000. The 
solution of decomposed nitroglycerine was diluted with distilled water until, 
on the addition of the starch reagent, a depth of blue was obtained precisely 
similar to that given by the strongest of the standard solutions of the nitrite. 
The solution was then diluted with an equal bulk of water, and, for the 
purpose of control, compared with the weaker standard solution. From the 
amount of dilution needed it was easy to estimate the quantity of nitrous acid 
present in the solution of the decomposed nitroglycerine. This method is 
only approximately correct, but it is the only method available. Any error 
was as far as possible eliminated by making the dilutions and comparisons with 
extreme care, and by occasionally repeating the estimation of the nitrous acid. 
The following were the results obtained. (The letters following the various 
specimens of nitroglycerine are for the purpose of identifying each specimen 
with its mode of preparation, which will be afterwards stated.) 

I. Nitroglycerine, A. — 11533 grms. dissolved in about 5 c.c. of alcohol, 
and treated with fully 1*5 grms. of caustic potash dissolved in about 
12 c.c. of alcohol. Boiled over water-bath for half an hour, water 
being added to replace the evaporated alcohol, and heating 
continued until the whole of the alcohol was driven off. Fluid 
diluted to 30 c.c. 1 c.c. of this was further diluted, and employed 
for the estimation of the nitrous acid. A dilution corresponding to 
1 of the original nitroglycerine in 620,000 of water was found to 
contain the same proportion of nitrous acid as the 1 in 1,000,000 
standard solution of nitrite of sodium. The nitroglycerine had, 

therefore, produced a quantity of nitrous anhydride - — \~- corre- 

— ■ 

sponding to 62 per cent, of the anhydride in Na.O.NO, or 34143 per 
cent, of the weight of the nitroglycerine. 

A second estimation of the nitrous acid in the same solution 
of decomposed nitroglycerine gave 35*244 per cent, of N 2 3 . 

II. Nitroglycerine, A. — 1 c.c. of a 10 per cent, solution heated to the 
boiling point with a small excess of alcoholic solution of potash ; 
diluted with two volumes of water and again heated to the boiling 
point, and the nitrous acid then estimated. 

N O 
The nitroglycerine yielded 3524 per cent, of 1 8 . 

III. Nitroglycerine, A. — Same in all respects as IT. 

The yield of nitrous anhydride was 35'24 per cent. 



CHEMISTRY OF NITROGLYCERINE. 



71 



IV. Nitroglycerine, A. — Same as II., except that caustic soda was used 
instead of caustic potash. The decomposition presented the same 
appearances as when potash was used. 

The yield of nitrous anhydride was 35 24 per cent. 

V. Nitroglycerine, A. — Same as II., but no heat applied, and fluid freely 
diluted with water two minutes after the addition of the potash. 
The yield of nitrous anhydride was 33 04 per cent. 

VI. Nitroglycerine, B. — 1 grm. dissolved in- about 6 c.c. of alcohol, and 
heated with 12 c.c. of 12| per cent, alcoholic solution of caustic 
potash. Boiled over water-bath to dissipate the alcohol, water 
being added to replace the alcohol. 

The yield of nitrous anhydride was 34*96 per cent. 

VII. Nitroglycerine, D. — 1 grm. dissolved in 15 c.c, of alcohol, and heated 
with excess of potash solution. 

The yield of nitrous anhydride was 34*41 per cent. Another 
estimation gave 34*96 per cent. 

VIII. Nitroglycerine, F. — Same proportions of nitroglycerine and alkali 
as in VII. 

The yield of nitrous anhydride was 34*96 per cent. 

IX. Nitroglycerine, G. — Same proportions as VII. 

The yield of nitrous anhydride was 35*24 per cent. 

X. Nitroglycerine, G. — Same proportions as IX. 

The yield of nitrous anhydride was 34*96 per cent. 

XL Nitroglycerine, N. — Same proportions as X. 

The yield of nitrous anhydride was 35*24 per cent. 

XII. Nitroglycerine (from Nobel's dynamite). — Same proportions as X. 
The yield of nitrous anhydride was 35*24 per cent. 

Summary of Estimations of Nitrous Acid in the Alkaline Decomposition- 
Products of Nitroglycerine. 





























No. of Analysis. 


1. 


II. 


III. 


IV. 


V. 


VI. 


VII. 


VIII. 


IX. 


X. 


XI. 


XII. 


Specimen 

of 

Nitroglycerine. 


A 


A 


A 


A 


A 


B 


D 


F 


G 


G 


N 


Dyna- 
mite. 


Percentage of 

Nitrous 
Anhydride. 


34143 


35-24 


35-24 


3524 


33-04 


34-96 


34-41 


34-96 


35-24 


34-96 


35-24 


35-24 



72 DR MATTHEW HAY ON THE 

These analyses are amply sufficient to show that the amount of nitrous acid 
formed during the alkaline decomposition of nitroglycerine is neither small 
nor variable ; and, assuming that nitroglycerine is a trinitrate of glyceryl, it 
corresponds remarkably with the supposition that two out of tLe three parts 
of nitric anhydride, which nitroglycerine contains, are reduced to nitrous 
anhydride ; for the trinitrate of glyceryl ought theoretically to yield, if so 
reduced, 33 48 per cent., an amount which agrees very closely with that 
actually obtained, if clue allowance be made for experimental error in a method 
which, although the best available, cannot claim to be exact. 

It is open to suggestion, reasoning alone from these estimations of nitrous acid, 

that nitroglycerine is perhaps a di-nitrite of glyceryl, or a mono-nitrate di-ni trite 

of glyceryl. As opposed to its being one or other of those bodies, the fact 

that specimens of nitroglycerine, as B and D, prepared in presence of urea, were 

found to yield the same proportion of nitrous acid as the others, is of importance. 

Another weighty objection to its being a nitrite is that on passing nitrous 

anhydride gas into glycerine no substance at all resembling nitroglycerine was 

obtainable ; although there was formed an oily liquid containing nitrous acid 

in combination, which, however, quickly decomposed in contact with water. 

This body has recently been investigated by Mr Masson,* and he believes it to 

be the tri-nitrite of glyceryl. It is not probable that the di-nitrite will possess 

greatly different properties. Were nitroglycerine the di-nitrite, it ought to 

yield a much higher proportion of nitrous acid than was actually obtained. 

For these and various other reasons, it is not the di-nitrite, and much less the 

tri-nitrite. As to the possibility of its being a mono-nitrate di-nitrite, the 

objection as to the yield of nitrous acid is not by any means strong. For 

N 
such a body ought theoretically to yield 30 - 89 per cent, of 2 9 3 (nitrous 

anhydride), an amount tolerably close to what was actually obtained. And 
amongst the alkaline decomposition products of nitroglycerine, it is not difficult 
to separate nitrate of potassium by crystallisation. But, on the other hand, 
the mono-nitrate di-nitrite ought to yield 21 - 5 per cent, of nitrogen, whereas, 
by actual experiment, Mr Masson and myself have found that nitroglycerine 
contains a much lower percentage of nitrogen. 

From these and other considerations, which will be referred to later on, it 
is impossible to avoid concluding that nitroglycerine is a tri-nitrate of glyceryl, 
and that two-thirds of its nitric acid is reduced to nitrous acid during the 
decomposition of the ether.t 

I shall now give a brief account of the other substances, besides nitrite of 
potassium, which are formed when an alcoholic solution of potash acts on an 
alcoholic solution of nitroglycerine. 

* Masson, Journ. Chem. Soc, August 1 883. 

+ Vide accompanying communication, on " The Elementary Composition of Nitroglycerine." 



CHEMISTRY OF NITROGLYCERINE. 73 

Nitrate of potassium is, as I have mentioned, present in considerable 
quantity, and with the nitrite constitutes the larger portion of the reddish-brown, 
partly viscid, partly crystalline precipitate, which is formed in the decomposing 
fluid. I have not estimated the nitrate quantitatively ; but there is every 
reason to believe, from the estimation of the total nitrogen by Schloesing's 
method and from other circumstances, that the amount of the nitric acid cor- 
responds very closely to one-third of the nitrogen present in nitroglycerine. 

But nitrite and nitrate of potassium are not the only substances formed. I 
have also proved the presence of acetate of potassium, oxalate of potassium, 
and, doubtfully, of formate of potassium, neither of the two latter appearing to 
be present in large quantity. There is also a small amount of ammonia, and of a 
reddish-brown, resinous body, which imparts the dark colour to the decomposing 
fluid. There is likewise present a very curious and very interesting substance, 
which possesses the unusual power of forming a firm jelly with a very large 
proportion of absolute alcohol. In contradiction to Railton and Williamson, 
and previous investigators, I have found no glycerine, or only the merest trace 
of it. This is a new and most important fact. 

In order to ascertain the presence and nature of these various decomposition- 
products, 6 67 grammes of pure nitroglycerine were decomposed with excess of 
potash in the usual manner, the mixture being allowed to boil for five minutes, 
and afterwards set aside for one day, to permit of the deposition of certain of 
the substances dissolved in the hot absolute alcohol. The supernatant fluid, 
which was transparent and of an orange colour, was then decanted, and the 
residue was again boiled with a fresh quantity of absolute alcohol, and again set 
aside for a day, when the alcohol was decanted and added to the previously 
decanted alcohol. This process was repeated a third time. The mixed alcoholic 
fluids ought to have contained the excess of caustic potash and the whole of 
the glycerine, were any present ; and in the deep reddish-brown residue I 
expected to find nearly all the colouring matter, and. all the salts insoluble in 
absolute alcohol, as the nitrite and nitrate of potassium. 

The mixed alcoholic fluids were neutralised with. alcoholic sulphuric acid in 
order to precipitate the potash as sulphate of potash. A voluminous white 
precipitate formed, which, after standing for some hours, was separated by 
filtration. The filtrate, although faintly acid, yielded another tolerably copious 
precipitate of sulphate of potash on the further addition of sulphuric acid, which 
was now added in distinct excess. Salts of potash were evidently present, dis- 
solved in the alcohol; certainly, amongst others, the nitrite and acetate, as proved 
by testing. The precipitate was again removed by filtration, and the alco- 
holic fluid was now distilled fractionally in order to remove the more volatile 
substances, as the alcohol and acetic, formic and nitrous acids, the less volatile 
glycerine, if present, remaining in the retort. Distillation was continued until 



74 DR MATTHEW HAY ON THE 

four-fifths of the fluid had been evaporated. An equal bulk of water was now 
added to the residue, and distillation was continued until the alcohol was almost 
completely expelled. The residue was now saturated with pure barium hydrate, 
in order to remove the sulphuric acid, and then filtered ; and the excess of 
barium was precipitated by a stream of carbonic acid gas, and the fluid was 
agaiu filtered. The filtrate was now evaporated over the water-bath, and was 
quickly reduced to five or six drops of a golden yellow viscid residue. Treated 
with absolute alcohol, in which glycerine is freely soluble, it at once hardened, 
and was almost entirely insoluble in alcohol. It evidently consisted in part of 
a barium salt, as ascertained by testing. The alcoholic solution or extract was 
filtered, and, on evaporation, yielded about one drop of a yellowish syrup, much 
more viscid than glycerine, and pungent rather than sweet to the taste. A few 
minutes' further drying dessicated it to a hard scale. The syrup gave merely 
the faintest odour of acrolein when heated with acid sulphate of potash. J 
therefore concluded that this residue, which ought to have contained the greater 
part of the glycerine, were any present, contained practically none of that sub- 
stance. The absence of glycerine from the alkaline decomposition products of 
nitroglycerine was confirmed by a second experiment, made with a still larger 
quantity of nitroglycerine, and in which no distillation was practised, and less 
opportunity therefore afforded for the decomposition or evaporation of the 
glycerine. 

The deep reddish-brown residue, laid aside at the commencement, after 
being well washed and extracted with boiling absolute alcohol, was next 
examined. Dried at 100° C. for 24 hours, it weighed 14*65 grms., and was 
probably not even then absolutely dry,, although very nearly so. The large 
amount of the residue is remarkable, as it weighs considerably more than the 
sum of the weights of the nitroglycerine decomposed, and of the potash neces- 
sary, according to Railton's equation, for the decomposition of the nitro- 
glycerine. This point will shortly receive an explanation. 

The dried residue was perfectly soluble in water, forming even with a large 
volume of water a deep reddish-brown solution. A portion of the residue was 
dissolved in boiling water, and, after standing for some hours, large needle- 
shaped crystals of nitrate of potassium separated, which by re-solution and 
re-crystallisation were obtained in a perfectly pure form, and distinctly recognised 
to be nitrate of potassium. From another measured portion of the residue it 
was attempted to remove the nitrite of potassium and formate of potassium (if 
present), by treatment with strong acetic acid, and extraction with boiling 
absolute alcohol, in order to remove the acetate of potash and free acids thus 
formed, and to obtain in a tolerably pure state the nitrate of potassium for the 
purpose of a quantitative determination ; but the method did not succeed. 

One-half of the original dried residue was next dissolved in water, and 



CHEMISTRY OF NITROGLYCERINE. 75 

treated with moderate excess of dilute sulphuric acid, and heated for a few 
minutes. Red fumes were evolved with brisk effervescence ; and a dark 
reddish-brown precipitate was formed, which evidently constituted the colouring 
matter of the decomposition products of nitroglycerine, although the colour 
was not wholly removed by the addition of the acid. The precipitate was 
collected on a filter, and washed with dilute acid and dried ; it weighed 0040 
gram. It was insoluble in acid solutions, but freely soluble in dilute solu- 
tions of alkalies or alkaline carbonates, and was of a resinoid character, and is 
probably similar in nature to aldehyde-resin, or even to caramel. 

As regards the peculiar alcohol-gelatinising body which I have mentioned 
as existing amongst the products of the alkaline decomposition pi nitro- 
glycerine, it was met with in the course of an examination of the decomposed 
products of 15 grms. of nitroglycerine, obtained in the usual way. The 
supernatant alcoholic fluid was treated with excess of dilute alcoholic sulphuric 
acid, in order to precipitate all the potash, both free and combined. The filtrate 
was afterwards neutralised, and the sulphuric acid precipitated by means of 
pure carbonate of barium. The evaporated filtrate yielded a residue which 
crystallised on cooling, and contained no glycerine, and which was very freely 
soluble in water without gelatinisation. It was also freely soluble in hot 
absolute alcohol ; but on allowing the solution to cool, even if the proportion of 
the residue to the alcohol was 1 to 20 or 30, the solution became a firm, partly 
crystalline-looking jelly, which could not be poured out of the test-tube in which 
it formed. This body, whatever be its exact constitution, is certainly a very 
exceptional organic substance, and deserves further examination. 

No gases are generated when potash acts on nitroglycerine in alcoholic 
solution. This was ascertained by placing the solution of nitroglycerine in a 
retort connected with a tube inverted over mercury, and boiling to drive out 
all the air. Alcoholic potash was then added, precautions being taken to 
prevent the simultaneous admission of air, and the boiling was continued for 
some time without any gas being formed. 

These are the products formed when alcohol is the medium through which 
the potash attacks the nitroglycerine. Similar products are obtained when 
water is employed, and the only apparent difference is that, on account of the 
very sparing solubility of nitroglycerine in water, the decomposition proceeds 
with great slowness, fully two hours' boiling over the water-bath being required 
to effect the decomposition of one gram, of nitroglycerine in a strong solu- 
tion of pure potash. Less red colouring matter is formed than when alcohol is 
employed, and much more oxalic acid seems to be produced ; but the amount 
of nitrous acid is the same. 

From this detailed account of the decomposition of nitroglycerine by caustic 
potash, it will be seen that the usual equation is very, far from representing 

VOL. XXXII. PART I. . N 



76 DR MATTHEW HAY ON THE 

what actually occurs. It is almost regarded as a fixed law in the chemical 
decomposition of compound ethers by alkalies, that the alkali unites with the 
acid of the ether and liberates the alcohol. This does not appear to be the 
case with nitroglycerine. For no glycerine is formed, and the acid is in great 
part reduced. But there is no doubt that the reduction of the greater portion 
of the acid is to be associated with the disappearance of the glycerine, which is 
evidently oxidised by the oxygen lost by the acid. Therefore, instead of 
glycerine, we have oxidation products of it, as acetic acid, oxalic acid, formic 
acid, &c. When nitroglycerine is being decomposed by potash, nitric acid and 
glycerine or glyceryl occur in a nascent and very active condition, the one as a 
powerful oxidising substance, the other as a readily oxidisable substance. As 
a consequence they act on each other, and two out of the three molecules of 
the nitric acid part each with an atom of oxygen to the glycerine or glyceryl, 
and this amount of oxygen is sufficient to completely oxidise and break up the 
glycerine, mostly, if not entirely, into certain organic acids, which, of course, 
will combine with a portion of the excess of the alkali used for the decomposi- 
tion. That is one view ; but there is another view, according to which the 
caustic potash may be regarded as taking an active part in the decomposition 
of the nascent glyceryl. When pure glycerine is melted with potash, it is well- 
known that acetate and formate of potash are produced along with free 
hydrogen." The action is represented by the equation, — - 

C 3 H 5 (OH) 3 + 2KOH = KO. CHO + KO. C. 2 H 3 + OH 2 + 2H 2 . 

The decomposition effected by potash under these conditions may occur even 
in dilute solution if the glycerine be in a nascent state, more particularly if 
there be present at the same instant a highly oxidising body like nascent nitric 
acid, which is promoting the same form of decomposition, and is ready to grasp 
the nascent hydrogen. The amount of hydrogen set free is precisely the 
quantity needed to reduce two -thirds of the nitric acid of the nitroglycerine, 
and the other decomposition products of the equation given correspond toler- 
ably closely with those actually ascertained to be formed. But if such a 
decomposition occurs, it implies that five, not three, molecules of hydrate of 
potash are required to decompose one molecule of nitroglycerine. In accord- 
ance with these views the action of caustic potash on nitroglycerine may be 
represented thus : — 



(1) C 3 H 5 -3(0-N0 2 ) + 3KOH = C 3 H 5 -(OH) 3 + 3(K-0-NO ? ). 

Nitroglycerine. Potash. Glycerine. Potassium 

Nitrate. 

(2) C. j H,-(OH) 3 -f-2KOH=KO-CHO-fKO-C 2 H :j O- r -OH 2 + 2H 

Glycerine. Potash. Potassium Potassium Water. Hydn 

Formate. Acetate. 

* Dumas et Stas, Ann. Chim. Plujs., lxxiii., 148. 



(3) 



CHEMISTRY OF NITROGLYCERINE. 



3.(KO.N0 2 ) + 2H s = KO.N0 5 + (2KO.NO) + 20H 2 . 

Potassium Hydro- Potassium Potassium Water. , 

Nitrate. gen. Nitrate. Nitrite. 



77 



or, combining these stages of the supposed reaction into one equation : — 



(4) C 3 H 5 . 3 (0 . N0 2 ) + 5K0H = KO . N0 2 + 2(K0 . NO) + KO . CHO + KO . C 2 H 3 + 30H 2 . 

Nitroglycerine. Potash. Potassium Potassium Potassium Potassium Water. 



Nitrate. 



Nitrite. 



Formate. 



Acetate. 



In equation (1) it might have been more in harmony with the view ad- 
vanced that the glycerine should have been represented as glyceryl and water, 
to indicate more completely its nascent state. 

There is every reason to believe that equation (4) is substantially and 
approximately correct, although in respect of the oxidation products of 
glycerine these may vary in their nature and proportions. Besides being in 
accordance with the results of the examination of the products of decomposi- 
tion, it is supported, as regards the amount of potash required, by the following- 
experiments : — ■ 

According to Railton's equation, one part of nitroglycerine requires for its 
complete decomposition 0741 parts of potassium hydrate ; according to the 
equation just given the proportion is as 1 : 1-235. If less of potash is used than 
in the latter proportion, then, if the latter equation be correct, complete decom- 
position will not occur, and a quantity of nitrous acid will be produced corre- 
sponding to the amount of potash employed ; and the solution of the products 
of decomposition will remain neutral until more than the requisite proportion 
of potash (1-235 to 1) has been added. In the following four experiments 
nitroglycerine, F., was employed in every instance, and a certain quantity of it 
was dissolved in alcohol and decomposed by an alcoholic solution of a given 
weight of pure potash, freshly crystallised from* alcohol, and as free as possible 
from carbonate ; the mixture being boiled for ten minutes, diluted with water, 
and again boiled for ten minutes. 



No. of 
Experiment. 


Weight of 
Nitroglycerine. 


Weight of 
Potassium 
Hydrate. 


Yield of Nitrous Anhydride, 

expressed as percentage of 

Nitroglycerine used. 


Reaction of Decom- 
posed Fluid. 


I. 

II. 

III. 

IV. 


Grms. 

1 
1 
1 
1 


Grms. 

80 
1-00 
1-24 
1-50 


Calculated accord- 
ing to Author's 
equation. 


Found; 


Neutral. 

Neutral. 

f Very slightly 
( alkaline. 

Alkaline. 


21-68 
2711 
33-48 
33-48 


23-23 
28-68 
34-69 
34-69 



DR MATTHEW HAY ON THE 



The degree of alkalinity of (IV.) was ascertained by titration with a stand- 
ard solution of sulphuric acid (30 in 1000). 62 c.c. of standard acid were 
required for complete neutralisation, which is equivalent to 0203 grms. of 
potassium hydrate, which, subtracted from 1-50 grms., the quantity of potash 
originally added, gives 1-297 grms. as the amount of potash actually used up, 
or a little more than the theoretical quantity. It is noteworthy in these 
experiments that where less than five molecules of potash, although more than 
three, were added to one of nitroglycerine, a quantity of nitroglycerine could 
be observed to remain unclecomposed, as it was precipitated on the addition of 
water to the alcoholic mixture, proving that when potash acts on nitroglycerine 
in presence of excess of the latter, according to the equation I have adopted, 
the potash is used up in thoroughly decomposing each molecule of the nitro- 
glycerine, and does not partially decompose a greater number of molecules. 
The respective yields of nitrous acid are alone sufficient to prove this. 

The amount of potash required for the decomposition of nitroglycerine is 
interesting in connection with a method described by Beckerhinn # a few years 
ago for the estimation of the degree of acidification of the ether, whether tri-, 
di-, or mono-nitrate, in which, after adding what he considered to be excess of 
caustic potash, he titrated the excess with normal oxalic acid. But his calcula- 
tions were based on the accuracy of Eailton's equation. It is very difficult, 
therefore, to understand how he could possibly have obtained satisfactory results, 
although he claimed to have done so, and quoted two analyses. In the follow- 
ing year Hess and Schwab t denied the correctness of his method, and made 
analyses according to it, but obtained widely different results, yet still acknow- 
ledging Eailton's formula, and ascribing the faultiness of the method to various 
minor circumstances. 

Action of Ammonia. — The volatile alkali seems to act on nitroglycerine in 
the same manner as the fixed alkalies, but not so energetically. When excess 
of strong ammonia was added to an alcoholic solution of nitroglycerine, there 
was no immediate decomposition of the nitroglycerine, as is the case when 
potash or soda is added. The resultant mixture remained colourless and 
showed no precipitate. It was then placed over the water-bath and heated all 
but to ebullition for one hour ; and in order to preserve excess of ammonia, more 
of the reagent was added from time to time. It now gradually assumed a deep 
reddish-brown colour, almost deeper than that observed in decomposition with 
potash. The maximum intensity of colour was reached after half an hour's 
heating, so that ammonia acts much more slowly than potash. The amount of 
nitrons anhydride obtained was equivalent to 345 per cent, of the nitroglycerine 

• Bbokebhhw, Sttzungsb. d. Wien. Akad., Bd. lxxiii. (1870), Abth. 2, S. 235. 
f JlEsa u. Schwab, Ibid., Bd. lxxv. (1877), Abth. 1, S. 702. 



CHEMISTRY OF NITROGLYCERINE. 79 

used, or a proportion exactly similar to that produced by the action of a fixed 
alkali.'"" 

Action of Alkaline Carbonates. — Nitroglycerine was dissolved in slightly 
diluted alcohol in order to permit the solution in it of carbonate of potash, 
which was afterwards added in the form of a concentrated aqueous solution. 
The mixture slowly assumed a reddish colour even in the cold. Heated over 
the water-bath, the nitroglycerine tolerably rapidly underwent decomposition, 
and the fluid became of a fairly deep reddish-brown colour. The. fluid was 
heated for one hour, and water was added as the alcohol became evaporated. 
The yield of nitrous anhydride was 35*24 per cent., or the same as when 
caustic potash is used. In a second experiment the yield was exactly the 
same. Using a five per cent, alcoholic solution of nitroglycerine, and boiling 
it with excess of carbonate of potash, it was ascertained that complete 
decomposition occurs in about ten minutes. 

Action of Phosphate of Soda fNa. 2 HPO J. — This salt is acid in constitution, 
but alkaline in reaction. Added in concentrated aqueous solution to a one 
per cent, alcoholic solution of nitroglycerine, and heated over the water-bath, the 
phosphate commenced to decompose the nitroglycerine three to four minutes 
after the mixture was fully heated, as was evidenced by the appearance of a 
yellowish tint gradually deepening to an orange-red. After heating for an 
hour and a half, slightly diluted alcohol being added occasionally, a yield of 
1376 per cent, of nitrous anhydride was obtained. In another experiment, 
after heating a similar mixture for forty minutes, 13*21 per cent, of nitrous 
anhydride was obtained. On both occasions the nitrous acid was estimated 
in one half of the fluid, and it was observed, in diluting the fluid with 
water, that a considerable amount of nitroglycerine was precipitated. In 
the second experiment, by adding potash to the remaining half of the fluid, 
and heating for a few minutes, and then estimating the nitrous acid, 34*41 per 
cent, of nitrous anhydride was obtained, proving that no nitrous acid had been 
set free by the phosphate of soda, which, in the absence of sufficient alkali, 

* It is somewhat remarkable that the yield of nitrous acid was as g^eat as when a fixed alkali 
was used ; since it is well known that a solution of nitrite of ammonia readily undergoes decom- 
position when heated ; and it was to be expected that the estimated yield of nitrous acid would have 
been diminished by the occurrence of such a decomposition in the heated fluid. In order to make 
certain that the result obtained was correct, and that under the conditions of the experiment such a 
decomposition did not occur, or occurred only to a limited extent, I have, since the paper was read, 
repeated the experiment. This I have done on two occasions, and with separate quantities of pure 
nitroglycerine. On the first occasion only 2 9 "6 per cent, of nitrous anhydride Avas obtained, but, on 
the second, 34.1 per cent., or very nearly what was obtained inthe experiment recorded in the text. 
The nitrite of ammonia formed by the splitting up of the nitroglycerine would appear, therefore, to 
undergo very little decomposition under the conditions in which it is placed. This may be due to 
the excess of free ammonia always maintained in the decomposing mixture, or to the low degree of 
heat applied, as, in order to prevent the rapid escape of gaseous ammonia, heat was applied short of 
ebullition of the fluid, or, more properly, of the escape of ammonia in the form of bubbles of gas ; or 
•it may be that the highly concentrated alcohol in which the nitroglycerine was dissolved hindered the 
decomposition of the nitrite. 



80 DR MATTHEW HAY ON THE 

might have been decomposed into nitric acid and nitric oxide, or evaporated 
off'. This form of control-analysis is the more necessary when the salt or 
substance employed to act on the nitroglycerine is neutral ; and in such 
circumstances I have always made use of it. 

Phosphate of soda appears, therefore, to act on nitroglycerine in much the same 
manner as alkalies and alkaline carbonates, only very much less powerfully. 

x I ction of Chloride of Sodium. — Excess of a concentrated solution of the pure 
salt was mixed with a one per cent, alcoholic solution of nitroglycerine. The 
salt was not precipitated, as the alcohol contained a little water. The mixture 
was heated for thirty -five minutes. There was no perceptible change of colour, 
and the quantity of nitrous acid did not amount to more than a fraction of a 
per cent, of the nitroglycerine used. The starch reagent yielded no blue 
colour with the fluid until sulphurie acid was added. The trace of nitrous acid 
Mas therefore present as a nitrite. One half of the fluid was treated with 
potash, and from it was procured an amount of nitrous anhydride correspond- 
ing to 3525 per cent, of the nitroglycerine. The chloride of sodium had not, 
therefore, decomposed the nitroglycerine and lost the nitrous acid by 
decomposition or evaporation. 

Chloride of sodium possesses, therefore, extremely little action on nitro- 
glycerine. 

Action of Hydrochloric Acid. — 1*6 c.c. of the strong acid were diluted with 
2 c.c. of water and added to 10 c.c. of a one per cent, alcoholic solution of 
nitroglycerine ; and the mixture was heated over the water-bath for half an 
hour. It was then found to contain a trace of nitrous acid, not exceeding a 
small fraction of a per cent, of the nitroglycerine. One half of the fluid, 
heated with excess of caustic potash, and thus completely decomposed, yielded 
nitrous anhydride corresponding to 13 5 per cent, of the nitroglycerine. 
This showed that the hydrochloric acid had decomposed about 39 .per cent, 
of the nitroglycerine, but whether with the formation of nitrous acid, it is 
quite impossible to say. For even had nitrous acid been formed, it would have 
been driven off by the boiling, or decomposed in contact with the water of 
the fluid. 

Hydrochloric acid, therefore, in large excess, decomposes nitroglycerine 
much more slowly than a caustic alkali or even an alkaline carbonate, and not 
much more quickly than phosphate of soda. 

Art ion of Sulphuric Acid. — 0*5 c.c. of strong sulphuric acid was diluted 
with 1 c.c. of water, and mixed with 10 c.c. of a one per cent, solution of 
nitroglycerine, and heated for half an hour. At the end of this period the 
fluid did not contain more than the merest trace of nitrous acid. One half 
of the fluid, boiled with potash, yielded nitrous anhydride corresponding to 
297 per cent, of the nitroglycerine. The sulphuric acid had, accordingly, 
decomposed 11*3 per cent, of the nitroglycerine employed. 



CHEMISTRY OF NITROGLYCERINE. 81 

Sulphuric acid, in the proportion used, would appear, therefore, to act less 
energetically than hydrochloric acid on nitroglycerine. Concentrated sulphuric 
acid in the cold seems to have almost no action, as is proved by the method 
of the preparation of nitroglycerine. 

Action of Sulphuretted Hydrogen. — According to De Vrij,* an ethereal 
solution of nitroglycerine is readily decomposed by sulphuretted hydrogen with 
a copious precipitation of sulphur. 

In order to test the truth of this observation, I submitted two ten per 
cent, solutions of nitroglycerine — the one in absolute alcohol, the other in 
ether — to the action of a stream of sulphuretted hydrogen gas. But although 
the gas was allowed to pass in a rapid stream through each solution for fifteen 
minutes, yet not the slightest trace of decomposition occurred, as was evidenced 
by no change of colour, and the absence of nitrous acid and precipitated sulphur 
and other decomposition products ; even although, in the case of the alcoholic 
solution, its temperature was raised to near the boiling point and the gas passed 
for fifteen minutes longer. Nitroglycerine was precipitated abundantly from 
both solutions on the addition of water. These experiments were more than 
once made, and always with the same result. 

It must, therefore, be concluded, that sulphuretted hydrogen has no action, 
or at most a very slow action, on pure nitroglycerine. The opposite experience 
of De Vrij was probably due to his having used an impure nitroglycerine. 

Action of Alkaline Sulphides. — These act very energetically on nitro- 
glycerine, and decompose it, if in alcoholic solution, as rapidly as alkalies alone 
do. On adding a solution of ordinary sulphide of potassium, or sulphide of 
ammonium, to an alcoholic solution of nitroglycerine, the mixture quickly 
assumes a deep reddish-brown colour, and its temperature rises ; and the 
action of the sulphide is completed with a sudden and most abundant 
precipitation of sulphur in every part of the mixture simultaneously. No gas 
is given off; and, contrary to expectation, after being boiled with excess of 
the sulphide for half an hour, filtered to remove the sulphur, and treated with 
acetate of lead and again filtered to remove the sulphuretted hydrogen of the 
sulphide, it yielded evidence of the presence of nitrous acid to the extent of a 
little less than half the proportion yielded by a purely alkaline decomposition. 
It would appear, therefore, that the whole of the nitrous acid set free in the 
decomposition of the nitroglycerine by the alkali of the sulphide is not acted 
on by the sulphuretted hydrogen of the sulphide. For we may assume, since 
sulphuretted hydrogen does not of itself attack nitroglycerine, that it is the 
alkali of the sulphide which takes the initial step in the decomposition of the 
nitroglycerine ; the sulphuretted hydrogen playing a subsidiary part, and merely 
acting on the nascent products of the decomposition effected by the alkali. 

* De Vrij, Journ. PTiarm. [3], xxviii., 3 ; and Gmelin's Handbook of Chemistry, x. p. 562. 



82 DR MATTHEW HAY ON THE 

But why the whole of the nascent nitrous acid should not thus be decomposed 
by the sulphuretted hydrogen I do not, in the meantime, attempt to explain, 
beyond suggesting that the nascent nitrous acid may in part combine with 
the alkali ; and, once so united, it is incapable of being acted on by the 
sulphuretted hydrogen. 

But the sulphuretted hydrogen does not play an altogether passive part in 
the actual decomposition of the nitroglycerine itself, for when an aqueous 
solution of an alkaline sulphide, such as potassium sulphide or ammonium 
sulphide, is poured over pure undissolved nitroglycerine, and the mixture 
vigorously shaken, the solution gradually becomes reddish, and the tempera- 
ture rises, and apparently, when the temperature has risen sufficiently, the 
whole or nearly the whole of the nitroglycerine suddenly decomposes with a 
copious formation of sulphur. In fact, the nitroglycerine seems to become 
suddenly converted into a mass of sulphur. It will be remembered that when 
potash alone is allowed to act on nitroglycerine under similar circumstances, 
the decomposition proceeds very slowly. The presence, therefore, of 
sulphuretted hydrogen very greatly promotes the decomposition of nitro- 
glycerine ; but in what particular manner I have not endeavoured to ascertain. 

Action of Water. — In order to ascertain to what extent water when boiled 
with nitroglycerine is capable of deconvposing it, a given quantity of a saturated 
aqueous, and, owing to the insolubility of nitroglycerine in water, a necessarily 
weak, solution of nitroglycerine was heated over the water-bath. After ten 
minutes 1 active heating, the fluid exhibited no signs of decomposition, and con- 
tained no trace of nitrous acid. It was then continuously heated for three 
hours. It still remained colourless, and on the addition of starch and iodide of 
potassium gave no blue ; but when these reagents were added along with 
dilute sulphuric acid, a distinct blue was obtained. The nitrous acid present 
was evidently combined with some other decomposition product of the nitro- 
glycerine ; it was estimated and found to amount to 17 per cent, of the whole 
nitroglycerine employed. A given portion of the fluid was heated with potash, 
in order to learn how much of the nitroglycerine remained undecomposed, and 
a quantity of nitrous acid (nitrous anhydride) was obtained, equivalent to 8*88 
per cent, of the whole nitroglycerine ; from which it is to be concluded that 
73 '48 per cent, of the nitroglycerine had been decomposed by heating with 
water for three hours. It is to be considered that a portion of this may have 
been lost by simple evaporation, although this was to a certain extent avoided 
by heating in a long-necked Florence flask. 

Action of Alcohol. — A one per cent, solution of nitroglycerine in absolute 
alcohol was heated over the water-bath for one hour, the alcohol being renewed 
from time to time. There was no change in colour, and nitrous acid could not 
be detected, even when sulphuric acid was added along with the usual reagents. 
A portion of the fluid was decomposed with potash, and the nitrous anhydride 



CHEMISTRY OF NITROGLYCERINE. 83 

obtained was found to be equivalent to 33 45 per cent, of the whole nitro- 
glycerine, proving that the nitroglycerine had not been apparently decomposed 
by heating with alcohol. 

From this it is evident that the alcohol used as a menstruum in ascertaining 
the action of other substances on nitroglycerine did not of itself aid in the 
decomposition of the nitroglycerine. 

Preparation of Nitroglycerine. — After I had observed that nitroglycerine 
yielded, when decomposed with an alkali, a large amount of nitrous acid, and being 
fully sensible of the insufficiency of existing analyses to determine the elementary 
composition of nitroglycerine, doubts arose in my mind, as I have already 
stated, as to whether nitroglycerine was actually a tri-nitrate of glyceryl. I 
have already given some important reasons in connection with its alkaline 
decomposition products for regarding it as the tri-nitrate, and not as any form 
of a nitrite. But I have thought it advisable to supply what additional proof 
could be obtained of its composition from a consideration of the yield of nitro- 
glycerine from a given weight of glycerine. For this purpose I prepared nitro- 
glycerine with various proportions of glycerine and acids, in order to ascertain 
the highest possible yield of nitroglycerine. Another important object which I 
had at the same time in view was to learn how far such variations in the method 
of the preparation of nitroglycerine might affect its composition. The latter 
object was very desirable, owing to the very discrepant statements which have 
been made by previous investigators as to nitroglycerine consisting entirely of 
tri-nitrate of glyceryl, or of a mixture of the tri-nitrate with the di-nitrate and 
mono-nitrate. 

In the preparation of the nitroglycerine, Price's pure glycerine, dried for 
six hours in the air-bath at a temperature of 120°C, was always employed ; the 
specific gravity, after drying, was 1260 at 14°C. The acids were each of two 
strengths — nitric acid, of a specific gravity of 1*422 (referred to as strong nitric 
in what follows), and 1/494 (referred to as fuming nitric acid) : sulphuric acid, 
of a specific gravity of 1-844 (referred to as strong sulphuric acid), and 1*984 
(referred to as fuming sulphuric acid) ; all at 15*5°C. In every instance the 
nitric and sulphuric acids were first mixed and placed in a vessel containing 
salt and ice, and cooled to below 0°C. In certain cases where urea was also 
used, it was added to the nitric acid previous to mixture with the sulphuric 
acid. Into the cooled mixture of the acids the glycerine was slowly dropped 
and well mixed by constant stirring, the temperature, as ascertained by a ther- 
mometer, never being permitted to rise above 10°C. After standing for a 
variable time, the mixture was poured into a large and measured quantity of 
cold water, when the nitroglycerine was precipitated. It was now very care- 
fully collected, after thorough stirring with the water, and was in this slightly 
impure state dried in the air-bath at 70°C. It dried quickly, but assumed a 
yellowish tint, and had a pungent acid odour. The weight of the dried nitro-, 

VOL. XXXII. PART I. O 



84 



DR MATTHEW HAY ON THE 



glycerine, increased by the weight of the nitroglycerine known to be lost by 
solution in the water into which it had been thrown, and which was calculated 
from a solubility of 1 in 800, gave the total yield of nitroglycerine. The nitro- 
glycerine before being used for any other purpose, as for analysis, was thor- 
oughly shaken with successive quantities of distilled water until it was perfectly 
pure. The first precipitation and washing was, I am satisfied, quite sufficient 
to remove by far the largest part of the impurities, and the trace of these left 
did not interfere to any noteworthy extent with the actual weight of the nitro- 
glycerine. In certain cases I checked the weight of the raw nitroglycerine by 
weighing the product after it had been thoroughly purified, and, again allowing 
for loss by washing, according to the quantity of water used, I obtained almost 
the same weights. A note of the time for which the mixture of the acids and 
glycerine was allowed to stand before being thrown into water was always kept. 



Figure 

o'f 

Reference 

for the 
Various 
Products. 


Weight 

of 

Glycerine. 

Gi-ms. 


Weight of Nitric 
Acid. 


Weight of 
Sulphuric Acid. 


Time 

of 

Standing 

after 
complete 
Mixture. 


Yield of 
Nitroglycerine. 


Strong. 
Grms. 


Fuming. 
Grms. 


Strong. 
Grms. 


Fuming. 
Grms. 


Absolute. 
Grms. 


Percentage. 


A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

J. 

K 

L. 

M. 

N. 


12-4 

6-1 
10-4 

8-8 
10-2 
108 
10-6 

9-4 
10-2 

9-6 
10-3 
10-5 
10-25 
10-0 


urea, 2 grms. 

30 

25 
30 
30 
30 

30 


30 
15 

urea, 1 grm. 
urea,r5grm. 

20 
20 

30 
30 
30 
30 


75 
30 
30 
50 
60 
90 
90 
20 
10 
30 
90 
30 
20 
60 


20 
30 

30 

40 


10 mins. 

8 „ 

5 „ 

5 „ 

5 „ 

5 „ 
60 „ 
30 „ 
30 „ 
30 ., 
30 „ 
30 „ 
50 „ 
30 „ 


1-7 

9-486 
16-71 
18-79 
19-11 
19-06 
18-80 

2-89 
23-40 
24-50 
23-75 
23-40 


16-3 

107-8 
103-8 
175-6 
180-2 
202-7 
184-3 
30-1 
2271 
233-3 
231-7 
234-0 



The specific gravity of each nitroglycerine was taken, and was found to vary 
from 1*601 to 1*604, depending on the temperature. From this fact alone, of 
the close agreement in specific gravity exhibited by the various products, it 
might be fairly concluded that they were all one and the same body. Their 
uniformity has, however, been more certainly proved by their all having been 
ascertained to contain the same percentage of nitrogen.* Indeed, in whatever 
way tested, whether as regards specific gravity, yield of nitrogen and of nitrous 
acid, and behaviour towards solvents, they were all found to agree precisely. 
The great difference in the amounts of the various products cannot therefore be 
regarded as being due to a difference in the nitroglycerine. It seems to be 
almost entirely caused by the differences in the quality and proportion of the 
* Vide TI.w and Masson's Paper on "The Elementary Composition of Nitroglycerine." 



CHEMISTRY OF NITROGLYCERINE. 85 

acids. The highest yield of nitroglycerine is that of N., where 234 parts of 
nitroglycerine were procured from 100 parts of glycerine. Now, glycerine, 
C 3 H 3 .(OH) 3 , ought theoretically to produce 246 per cent, of tri-nitrate of 
glyceryl, C 3 H 5 .3(O.N0 2 ). Making allowance for inevitable loss from 
various intelligible causes, it may, therefore, be fairly deduced that the experi- 
mental yield of nitroglycerine strongly favours nitroglycerine being regarded 
as the tri-nitrate. If it were the tri-nitrite, C 3 H 5 .3(0.NO), the theoretical 
yield would be 194 per cent. ; if the di-nitrite, C 3 H 5 .H0.2(O.NO), 163 per 
cent.; and if the mono-nitrate di-nitrite, C 3 H 5 .(O.N0 2 ).2(O.NO), 211 per cent. 
The actual yield very distinctly exceeds any of these. 

With regard to the conclusions of practical and commercial importance 
which may be drawn from these various methods of preparing nitroglycerine, 
it is to be observed that there is a distinct advantage, as is generally recognised, 
in employing fuming nitric acid (compare (F) and (G) with (K) ) ; that where 
fuming nitric acid is used, no benefit is to be obtained from the employment of 
fuming sulphuric acid (compare (L) and (M) with (K) and (N) ); that two parts 
of ordinary sulphuric acid to one part of fuming nitric acid appears to give as 
good a yield as any other proportion of acids, and quite as large a yield as 
when more sulphuric acid is used (compare (N) with (K) ) ; and that the yield 
is not to any considerable extent increased by allowing the acids and glycerine 
to remain in contact for some time after mixture, as some chemists have 
advised (compare (F) with (G), and (L) with (M) ). 

Characters of Nitroglycerine. — I have been somewhat surprised to find 
that a large number of contradictory statements exist as to the ordinary physical 
characters of nitroglycerine. Whilst a few authors describe it as colourless, 
by others it is referred to as a pale yellow oil, even in the most authoritative 
modern works on Chemistry, as Fehling's Neues Handworterbuch der Chemie* 
and Beilstein's Handbuch der Organischen ChemieA Now nitroglycerine is per- 
fectly colourless when pure. As obtained from dynamite, it is certainty yellow, 
but the colour is due to decomposition having taken place, which, I believe, is 
to little or no extent spontaneous in character, but rather proceeds from the 
presence of a little of the weak soda which is invariably employed in the manu- 
facture of nitroglycerine for the purpose of removing the traces of the acids. 
The soda neutralises the acids, but it at the same time decomposes the nitro- 
glycerine, and imparts the colour so commonly ascribed to it as an inherent 
property. Nitroglycerine washed with distilled water has in my possession 
never become in the slightest degree coloured, even although kept in an open 
capsule, freely exposed to the air, but away from dust, for two months ; in 
stoppered bottles it has not during the last seven months showed the least sign of 
decomposition. Even in solution in water, or in alcohol, it keeps almost equally 
well. More than one author states that it decomposes and becomes red on 

* Bd. iii. 1878. f S. 529, 1881. 



86 DR HAY ON THE CHEMISTRY OF NITROGLYCERINE. 

being heated over the water-bath. I have heated pure nitroglycerine to the 
highest possible temperature over the water-bath for four hours, and have 
never observed the development of the slightest colour or decomposition. 
When it decomposes under such circumstances it probably contains free acid 
or alkali. Again, it is stated by Railton* that when placed in the bell-jar of 
the air-pump it rapidly undergoes decomposition. In the course of the investi- 
gation by Mr Masson and myself, we have kept nitroglycerine for twelve days 
in vacuo without its exhibiting the slightest signs of decomposition. The 
decomposition of Railton's preparation must have been due to its impurity. 

Nitroglycerine has no odour when cold, but emits a pungent odour when 
heated. Although odourless in the cold, it nevertheless seems to be under- 
going slight volatilisation ; for after working with it for a short time, and. without 
directly touching it with the fingers, I have generally experienced its physio- 
logical effect in a slight degree. Its taste is sweet, and not unlike that of 
glycerine, but is more pungent. 

As regards its solubility, 1 gram, dissolves in about 800 c.c. of water ; 
with difficulty in 3 c.c. of absolute alcohol, easily in 4 c.c. ; in 105 c.c. of 
rectified spirit (sp. gr. - 846) ; in 1 c.c. of methylic alcohol (sp. gr. , 814) ; in 
4 c.c. of methylated spirit (sp. gr. 0"830) ; in 18 c.c. of amylic alcohol; in every 
proportion in ether ; so also in chloroform, in glacial acetic acid, and in carbolic 
acid; in less than 1 c.c. of benzol; in 120 c.c. of carbon bisulphide; and to a 
very limited extent, if at all, in glycerine. 

Method of Estimating Nitroglycerine. — In cases where nitroglycerine 
cannot be estimated gravimetrically after extraction with one of its solvents, 
a method based on the evident constancy of the amount of the nitrous acid 
produced in its decomposition with potash may be safely adopted. I have 
made use of this method for ascertaining the degree of its solubility in water, 
and for other quantitative estimations in the course of this investigation, 
and it is not difficult to apply. The materials necessary are a standard 
solution of pure nitrite of sodium (titrated with permanganate) of the 
strength of 1 in 1,000,000, a well-boiled solution of starch and iodide of 
potassium, dilute sulphuric acid, and pure potash, ascertained to be free from 
nitrous acid. Heat the fluid containing the nitroglycerine with excess of 
potash, and dilute with water until, in comparison with the standard solution of 
nitrite of sodium, it yields a blue colour with the starch mixture and sulphuric 
acid of precisely the same depth. From the degree of dilution required the 
amount of nitrous anhydride present can be readily calculated, and this amount 

multiplied by 33 .^ g (33-48 being the percentage of nitrous anhydride yielded by 

nitroglycerine) will give the quantity of nitroglycerine. 

* Op. cit. 



( 87 ) 



VI. — The Elementary Composition of Nitroglycerine. By Matthew Hay, M.D., 

and Orme Masson, M.A., B.Sc. 

(Communicated by Professor Crum Browx. ) 

Nitroglycerine is commonly described as the tri-nitric ether of glyceryl, and 
the formula C 3 H 5 (O.N0 2 ) 3 is accorded to it. This theory of its composition 
is based (1) upon its mode of formation; (2) upon the statement, made by 
Railton, Williamson, and others, that it is decomposed by potash into 
potassium nitrate and glycerine ; (3) upon several estimations of the nitrogen 
which it contains, and one comparative estimation of its carbon. The second 
argument cannot be accepted, as it has been shown by one of us that the 
decomposition does not take place in the way stated ; * and the analytical 
results which have been obtained by the various investigators are so incomplete 
and mostly so imperfect, and differ so greatly among themselves, that they 
cannot be taken as affording any proof of the composition of the substance. It 
seemed to us, therefore, desirable that some accurate estimations should be 
obtained, not only of the nitrogen but of the carbon and hydrogen. A brief 
resume of previous analytical results will show that this is the case. 

Railton, t in 1855, attempted to estimate the relative quantities of carbon 
and nitrogen by Liebig's method. The ratio of the volume of carbonic acid to 
that of nitrogen required by the formula is 2:1. Railton obtained results 
varying from 2156 : 1 to 1*912 : 1 ; so that, although they are on the whole in 
favour of the formula, they cannot be regarded as satisfactory. He made no 
attempt to estimate the carbon and hydrogen absolutely, as he found it 
impossible to dry his nitroglycerine, even in an exhausted receiver, on account 
of its great tendency to decompose. This proves that the substance was 
impure, as we have found pure nitroglycerine to be perfectly stable in the air 
and in vacuo. 

Williamson,! in the following year, gave an account of the composition of 
nitroglycerine, which agrees so exactly with Railton's in every detail, that 
there can be no doubt that their experiments were made in conjunction, 
although published separately and without reference to each other. 

Hess, § in 1874, estimated the nitrogen in commercial nitroglycerine 

* See the preceding paper : " Contribution to the Chemistry of Nitroglycerine," by Matthew Hay. 
f Eailton, Quart. Jour. Chern. Soc, vol. vii. p. 222. 
J Williamson, Proc. Roy. Soc, vol. vii. p. 130. 
§ Hess, Zeitschr. f. anal Chem., 1874, S. 257. 

VOL. XXXII. PART I. • P 



88 MATTHEW HAY AND ORME MASSON ON THE 

obtained from various sources. He used different methods and got results 
varying from 137 to 16*6 per cent., the percentage required by the formula of 
glyceryl tri-nitrate being 18*5. From this he concluded that commercial nitro- 
glycerine contains the mono- and di-nitrate, as well as the tri-nitrate. 

Beckerhinn,* in 1876, described an extremely elaborate method for the 
estimation of the carbon and hydrogen, but gave no results. 

Hess and ScHWAB,t in 1877-78, made some nitrogen determinations by 
Dumas's method. In one sample they found 15*72 and 15*65 per cent., and in 
another (from Nobel's Zamky manufacture of 1872) they found 16*13, 1612, 
and 16*12 per cent., though this was the same liquid which four years earlier 
had yielded Hess only 14*0 per cent. 

Sauer and Ador,| in 1877, estimated by three methods the nitrogen in nitro- 
glycerine obtained from dynamite. First they used Reichardt's modification 
of Schloesing's method, after decomposing the liquid with potash, and obtained 
from 12*3 to 14 per cent. Next they tried the ignition with soda-lime process, 
but found that only 2 to 3 per cent, of the nitrogen was evolved as ammonia. 
Finally they made four determinations by Dumas's method, using nitroglycerine 
obtained from three different samples of dynamite ; and in this case they 
obtained from 18*35 to 18*52 per cent., which agrees very closely with the per- 
centage calculated from the formula, but differs widely from that obtained by 
Hess and Schwab by the same method. 

The nitroglycerine which we employed in our analyses was made by adding, 
drop by drop, one part by weight of Price's pure glycerine to a mixture of two 
parts of nitric acid (sp. gr. 1*49) and six parts of sulphuric acid (sp. gr. 1*84), 
the mixture being surrounded with ice and kept at a temperature never 
exceeding 10° C. Five minutes were allowed to elapse before pouring the 
mixture into water ; and the precipitated nitroglycerine was then well washed 
eight times with large volumes of distilled water, and dried for seven hours in 
an air-bath at a temperature of from 70° to 80° C. Finally, it was allowed to 
stand twelve days over sulphuric acid in the exhausted receiver of an air-pump. 
Not the slightest sign of decomposition ensued ; and it was found that the 
nitroglycerine, after standing one week in vacuo, had lost less than one-tenth 
per cent, of its weight, which shows that it was practically dry from the first. 
It was perfectly colourless and transparent. Its specific gravity at 14°*5C. 
was 1*601. 

The carbon and hydrogen were estimated by ignition in a tube closed and 
drawn out at one end and filled with copper oxide and metallic copper in the 
usual manner. At the termination of the ignition the drawn-out point was 

* Beckerhinn, Sitzgsber. Wien. Akad., Bd. lxxiii., Abth. ii. S. 240. 
t Hess u. Schwab, Ber. Deutsch. chem. Gesellschft., Bd. xi. S. 192. 
% Sauer u. Ador, Ibid., Bd. x. S. 1982. 



ELEMENTARY COMPOSITION OF NITROGLYCERINE. 



89 



broken, and a stream of oxygen was passed through to ensure the complete 
combustion of the carbon. In our first experiment the nitroglycerine was 
weighed out in a short glass tube, and this was dropped into the combustion 
tube ; but an explosion occurred at an early stage of the ignition, which, 
although damaging the furnace and slightly injuring one of us who happened 
at the moment to be within a few inches of the tube, satisfied us that the 
explosive force of the quantity of material employed (0*23 grm.) was not so 
great as to prevent our continuing the experiments with the adoption of very 
ordinary precautions. It was next attempted to burn the nitroglycerine in the 
form of dynamite, using pure and previously ignited Kieselguhr as the 
absorbent ; but this also gave rise to an explosion, though of greatly diminished 
violence. Ultimately it was found that the combustion could be performed 
without any risk of explosion by adopting the following method. A quantity 
of the liquid (from "2 to "4 grm.) was weighed out in a porcelain boat con- 
taining finely-divided copper oxide, and was then covered with another layer of 
the oxide. The boat was dropped into the combustion tube, and its contents 
were scraped out and well mixed up with the granulated copper oxide by 
means of a long bent copper wire. The tube was then filled up in the 
customary manner. The chief difficulty attending this method is to avoid the 
introduction of moisture by the copper oxide and consequent raising of the 
hydrogen percentage. The precautions taken against this were increased in 
each experiment, so that the last hydrogen determination is probably the most 
reliable, while the first is considerably too high. All the combustions were 
conducted with unusual slowness. The same means was employed for filling 
the tube in the nitrogen determinations by Dumas's method. 





Calculated. 


Found. 






I. 


II. 


in. 


IV. 


v. • 


L 3 , 


15-86 


16-05 


15-89 


15-80 




• . • 


H 5 , . 


2-20 


2-99 


2-40 


2-08 






N„ 


18-50 








17-93 


17-97 


9) . . . 


63-44 


... 


... 


... 


... 


... 



Two nitrogen determinations were also made with the same nitroglycerine 
before it had been placed in vacuo, and the results, though slightly higher, 
hardly warrant the belief that there was any difference in the composition. 
They were (1) 18-25 and (2) 18-06. 

We consider that the above figures prove nitroglycerine to be glyceryl 
tri-nitrate, the slight deficiency of nitrogen being possibly due to the presence 



00 MATTHEW HAY AND ORME MASSON ON THE 

of traces of impurities (oxidised derivatives of glycerine) irremovable by the 
water with which the nitroglycerine was washed. 

We have also estimated the nitrogen in other samples of nitroglycerine, 
prepared with different proportions of acid, in order to ascertain whether a 
difference in the method of preparation causes any corresponding difference in 
the composition of the liquid. The results show that it is not so. In these 
cases Dumas's method was not employed, but a modification of Schloesing's 
process, which we have found to give equally good results, in spite of the 
contrary experience of Hess and Schwab and of Sauer and Ador. 

The weighed quantity of nitroglycerine was dissolved in absolute alcohol 
and decomposed by boiling for ten minutes with excess of an alcoholic solution 
of caustic potash. Water was then added, and the whole of the alcohol was 
driven off by evaporation ; after which the fluid was made up to a given 
volume, of which a measured portion was taken for experiment. The volume 
of nitric oxide evolved by the reducing action of the ferrous chloride and 
hydrochloric acid (the reagents employed in Schloesing's method) was, in each 
case, compared with the volume of gas obtained under precisely the same 
conditions of temperature and pressure from a standard solution of pure 
potassium nitrate, aud also, in certain instances, of pure sodium nitrite ; and 
from these data the percentage of nitrogen was calculated. A correction is, 
however, necessary, inasmuch as a small portion of the nitrogen is always 
evolved as ammonia on boiling the nitroglycerine with potash. The amount 
of this was determined in a preliminary experiment, as follows : — 

1*1533 grm. of nitroglycerine was dissolved in 5 c.c. absolute alcohol and 
a solution of 1*5 grm. of potash in absolute alcohol added, the flask being 
immediately connected with a modified Boussingault's apparatus and then 
boiled. After half an hour an equal volume of water was added, and boiling 
then continued three-quarters of an hour more. The distillate was received 
into standard acid ; and, at the end of the operation, this was titrated with 
standard soda. By this means it was found that *0053 grm. of ammonia had 
been evolved ; so that nitroglycerine loses nitrogen during decomposition with 
potash to the extent of 0"38 per cent, of its weight. This amount was, 
therefore in each case, added to the percentage of nitrogen found by 
Schloesing's method. 

In the following table the letters in the second column refer to the various 
samples of nitroglycerine employed. A detailed description of their manu- 
facture will be found in the preceding paper,* where they are lettered in the 
same order. Experiment IX. was made with nitroglycerine obtained from 
a Nobel's dynamite cartridge by displacement with water and desiccation over 
the water-bath. 

* "A Contribution to the Chemistry of Nitroglycerine," by Matthew Hay. 



ELEMENTARY COMPOSITION OF NITROGLYCERINE. 



91 



No. of 


Nitroglycerine 


Percentage 


Corrected for loss 


Percentage 


Experiment, 


Employed. 


Nitrogen found. 


of NH 3 . 


Calculated. 


I. 


A 


17-77 


18-15 


\ 


II. 


A 


1747 


17-85 


III. 


A 


17-76 


18-14 




IV. 


B 


17-76 


18-14 




V. 


C 


17-76 


18-14 


> 18-50 


VI. 


F 


17-41 


17-79 




VII. 


J 


17-81 


18-19 




VIII. 


N 


17-73 


18-11 




IX. 


Nobel's 


17-77 


1815 


/ 



These figures agree closely not only with each other, but with those obtained 
by us by Dumas's method. Our analyses already given prove nitroglycerine 
to be glyceryl tri-nitrate : these analyses render it highly probable that it is 
invariable in composition, and that therefore the statements of some previous 
investigators, particularly those of Hess, are erroneous. If nitroglycerine at 
any time does contain the lower nitrates of glyceryl, it is probably owing to the 
nitroglycerine having been very imperfectly washed in the process of its 
manufacture. Nitroglycerine is only very slightly soluble in water ; glycerine 
is freely soluble in water ; and, reasoning from chemical analogies, it is highly 
probable that the intermediate nitrates possess intermediate degrees of 
solubility, which will readily permit of their removal by an ordinarily complete 
washing of the nitroglycerine with water, but may allow only of their partial 
removal if a limited quantity of water is used. According, however, to the 
published description of the various commercial processes for the preparation 
of nitroglycerine, the washing appears to be sufficiently thorough to remove 
the lower nitrates ; for the amount of washing necessary to remove traces of 
the free acid used in the manufacture of nitroglycerine is certainly quite 
sufficient to dissolve out the lower nitrates. 



VOL. XXXII. PART I. 



( 93 ) 



NIL — Report on the Tunicata collected during the Cruise of H. M.S. " Triton " in 
the Summer of 1882. By W. A. Herdman, D.Sc, Professor of Natural 
History in University College, Liverpool. (Plates XVI. to XX.) 

(Read 16th July 1883.) 

This collection was sent to me for examination some months ago by Mr 
Murray. It may be conveniently divided into two very natural groups : — 

1. Asciuiacea, including the forms dredged or trawled from the bottom 

of the sea. 

2. Thaliacea, including the free-swimming pelagic forms captured by 

the tow-net at or below the surface. 

The small group of Ascidiacea contains no Compound Ascidians, and only 
two* of the four families of Ascidia} Simplices known are represented in it. The 
one of these families (the Cynthiidae) is represented by a single species only, while 
the other (the Ascidiidse) contains the remaining three species, referred to the 
two genera Ascidia and Ciona. One of those species of Simple Ascidians 
(Ascidia tritonis) is new to science, the other three are well-known British 
forms. 

This little collection of Ascidiacea is chiefly interesting (1) on account of 
the depths at which the specimens were procured, and (2) on account of the 
locality being one in which the Ascidian fauna had not been previously investi- 
gated. Ascidia tritonis, though a new species, is not in any way aberrant or 
strikingly peculiar, and hence, as far as the Simple Ascidians of the collection 
go, the region explored by the " Triton " may readily be regarded as an exten- 
sion of the British fauna. 

The second group — -the Thaliacea — is a very considerable collection, as may 
be seen from the following list of the different localities. The most remarkable 
circumstance in regard to it is that, with the exception of two specimens of 
Salpa, the whole series is composed of one species, Doliolum denticulatum, of 
which between five and six thousand specimens were collected. 

List of " Triton " Thaliacea. 

1882. 
August 3rd— 4th. Surface. Doliolum denticulatum, about 100 specimens, 1 small one (2 mm. long). 
„ 4th. Tow-net at a depth of 12 fathoms. Dol. denticulatum, 8 specimens, in absolute 

alcohol. 
,, 4th — 5th. Tow-net at a depth of 12 fathoms. Dol. denticulatum, about 1000 specimens; and 
1 specimen of Saljpa runcinata (aggregate form). 

* See "Postscript," page 114. 
VOL. XXXII. PART I. R 



94 DR W. A. HERDMAN ON 

August 5th (Station 2). Nets at the weights and trawl, 530 fathoms. Dol. denticulatum, about 1000 
specimens ; alst i 6 specimens in absolute alcohol. 

,, 7th. Surface. Dol. denticulatum, about 30 specimens. 

„ 7th — 8th. Surface. „ 3 specimens, in absolute alcohol. 

„ 8th. Surface. „ 20 specimens. 

,, 9th. Tow-nets at a depth of 100 to 150 fathoms. Dol. denticulatum, 60 specimens ; 

also 20 in absolute alcohol. 

„ „ Tow-nets at trawl at a depth of 327 to 430 fathoms. Dol. denticulatum, 20 speci- 

mens. 

,, 13th — 30th. Surface to 40 fathoms. Dol. denticulatum, 9 specimens. 

„ 18th. Surface. Dol. denticulatum, 1 specimen; and 1 specimen of Salpa runcinata (soli- 

tary form). 

„ 20th. Surface. Dol. denticulatum, 1 large and 3 small (2-3 mm. long) specimens. 

,, ,, Tow-net at a depth of 40 fathoms. Dol. denticulatum, about 50 specimens. 

„ „ Tow-net at a depth of 300 fathoms. Dol. denticulatum, about 40 specimens. 

,, ,, Tow-nets with 400 fathoms of line out. Dol. denticulatum, 75 specimens. 

„ „ Tow-nets at a depth of 400 fathoms. Dol. denticidatum, 12 specimens. 

„ 21st. Surface. Dol. denticidatum, 1 specimen, stained brown, 

„ - „ Tow-net at a depth of 40 fathoms. Dol. denticidatum, about 50 specimens. 

,, „ Tow-nets from surface to 400 fathoms. ,, „ 80 „ 

„ „ „ at a depth of 600 „ „ ,, 50 „ 

,, 22nd. Tow-nets between surface and 40 ,, ,, 25 specimens. 

„ 22nd— 23rd. Surface, at night. „ 75 

„ 24th. Tow-nets at a depth of 40 fathoms. ,, 1 specimen. 

,, 28th. Surface. ,, 50 specimens. 

„ „ Surface down to 40 fathoms. ,, about 40 specimens. 

,, ,, Tow-nets at a depth of 40 fathoms. „ 30 specimens. 

„ 29th. Surface. Dol. denticulatum, 28 specimens, in osmic acid and absolute alcohol. 

„ „ „ about 100 „ picric „ 

„ „ „ „ 180 „ osmic 

„ „ „ „ 150 „ chromic „ 

„ ,, Tow-net at a depth of 5 to 10 fathoms. Dol. denticidatum, about 1200 specimens. 

„ ,, Tow-nets at a depth of 10 fathoms. Dol. denticulatum, about 150 specimens, in 

chromic acid. 

„ ,, Tow-nets at a depth of 13 fathoms. Dol. denticulatum, 1 specimen, in chromic 

acid. 

,, „ Tow-nets at a depth of 12 fathoms. Dol. denticulatum, about 100 specimens, in 

picric acid. 

„ ,, Tow-nets at a depth of 20 fathoms. Dol. denticidatum, about 100 specimens. 

„ 30th. „ „ 40 „ „ 200 

,, ,, Tow-nets with 400 fathoms of line out. Dol. denticulatum, about 130 specimens. 

,, „ Tow-nets at weights (Station 12), 580 fathoms. Dol. denticulatum, 50 specimens. 

„ 31st. Surface. Dol. denticulatum, 100 specimens. 

„ „ Surface down to 40 fathoms. Dol. denticidatum, about 100 specimens, one of 

them small (3 mm. long). 

,, ,, Tow-net at trawl (Station 13), depth 570 fathoms. Dol. denticulatum, 20 speci- 

mens. 

Also, obtained during the cruise of the "Knight Errant": — 

August 10th, 1880, From a depth of 20 fathoms. Salpa zonaria, 10 specimens. 

The localities of most of these dates, namely, 7, 7-8, 8, 9, 18, 20, 21, 29, and 



THE " TRITON " TUNICATA. 95 

30, are over the " Wyville-Thomson " ridge, 7, 7-8, 8, 9, and 30 being towards 
the NW. end, and 18, 20, 21, and 29 near the centre. 22 and 22-23 are 
situated in the " cold area " near its southern end ; while 24, 28, and 31 are 
in the " warm area " near the SE. end of the ridge. 3-4, 4, 4-5, and 5 are 
between the island of Rona and the southern end of the ridge. 



Order I.— ASCIDIACEA. 

Family Cynthiid^e. 

Polycarpa pomaria, Savigny (PI. XVII. figs. 5 and 6). 

I have referred a small specimen from Station 3 to this widely distributed 
and apparently highly variable species. I have not examined a sufficient 
number of specimens to be able to say much as to the range of variation from 
my own experience ; but from a comparison of the descriptions of other inves- 
tigators, it is obvious that this is one of those interesting forms out of which it 
is possible to make either one or half a dozen " species," according to the state 
of one's critical faculties. Traustedt* describes it as Sty da pomaria, and gives 
as synonymous Cynthia pomaria, Sav., C. coriacea, Alder, C. tuber osa, Macgill, 
and Polycarpa varians, Heller ; while HELLERt suggests that Cynthia sulcatula 
and C. granulata of Alder may also be varieties merely. 

There can be little doubt that Savigny's Cynthia polycarpa and C. pomaria 
are merely varieties of the one species now known as Polycarpa pomaria, 
Sav. ( = P. varians, Heller), and Cynthia tuberosa of Macgillivray is certainly 
the same species ; while Alder's Cynthia sulcatula and C. granulata may 
possibly be young individuals. But I cannot agree with Traustedt and 
Heller in regarding Cynthia coriacea, Alder and Hancock, as another variety. 
The description in Alder's Catalogue J states (1) that the ovaries are large and 
white, and line the mantle with cylindrical convolutions, and (2) that the 
branchial sac has about ten longitudinal folds, two important characters either 
of which would be sufficient evidence to exclude the species from the genus 
Polycarpa, while the second alone, if "about ten" may be taken as meaning 
more than eight, cuts it off even from the sub-family Styelinse. 

The Triton specimen, which is a small one (2 cm. in length, 1*6 cm. dorso- 
ventrally, and 12 cm. in thickness), was trawled at Station 3 (8th August 1882, 
at the NW. end of the Wyville-Thomson ridge, and north of the " warm area," 
bottom s. sh.) from 87 fathoms. Viewed from the side, it is rudely quadrate 

* Oversigt over defra Danmark og dets nordlige Bilande kjendte Ascidice Simplices. Vidensh. Meddel, 
Nat. For., Kjbbenbavn, 1880, p. 415. 

f Vntersuchungen uber die Tunicatendes Adriatisclien und Mittelmeeres, Abth. iii. p. 19, Wien, 1877. 
| Cat. Mar. Moll. Northumb. and Durbam, Trans. Tijnes. Nat. Field Club, vol. i. 1850. 



96 Dll W. A. HERDMAN ON 

rather than hemispherical in outline, the anterior end being truncated and 
almost as broad as the base of attachment. The most projecting point of the 
anterior end is placed midway between the two apertures, which are far apart, 
and distinctly upon the right side of the extremity (see PI. XVII. fig. 5). Probably 
on account of extreme contraction, they are also sessile, rather inconspicuous, 
and irregularly lobed. 

The test is thick, strong, and leathery ; greyish- white on the outer surface, 
and white in section. At the posterior end it has several root-like prolonga- 
tions from 1 to 12 cm. in length. The mantle is thick, strongly muscular, and 
closely united to the inner surface of the test. 

The branchial sac has eight very prominent folds, four upon each side. The 
two dorsal folds on each side are more closely placed than the ventral ones, 
and the clear spaces bordering the endostyle are considerably wider than those 
beside the dorsal lamina. As the branchial sac of this species has never, so 
far as I am aware, been figured, I give a view (PI. XVII. fig. 6) from the inside 
of a part showing two folds and the interspace in their natural relations, while 
at the right-hand side another interspace is represented as more exposed by the 
removal of the next fold. The sac is a very thick one, the folds being prominent, 
the internal longitudinal bars numerous, and the stigmata comparatively small. 
Occasional wider transverse vessels occur ; in some places (see fig., tr) they 
alternate regularly with three smaller ones {tr'). Delicate membranes dividing 
the meshes are only present here and there (tr"). At the base of each fold 
lies a series of large meshes (mh), each of which I found contained about 
six stigmata. Heller mentions meshes with ten to twelve stigmata each ; I 
found such only in the series adjoining the endostyle. 

The simple tentacles are numerous and closely placed. The dorsal tubercle 
is small and nearly circular in outline, being slightly elongated laterally. The 
aperture is anterior, and both horns are coiled inwards. 

The margin of the anus is expanded, and cleft into a number of blunt pro- 
cesses. 

The yellow polycarps and grey endocarps are so numerous as almost com- 
pletely to hide the inner surface of the mantle. 



Family Ascidiid^e. 

Ascidia tritonis, n. sp. (Plate XVI.). 

External Appearance. — Shape ovate, flattened laterally, attached by posterior 
half of left side, especially towards the ventral edge ; anterior end rather 
narrower than posterior but blunt. Dorsal edge slightly more convex than 
ventral. Branchial aperture terminal, sessile, wide, lobes distinct. Atrial 



THE "TKITON" TUNICATA. 97 

aperture on dorsal edge, halfway from anterior to posterior end, sessile, wide, 
indistinct lobed. Surface even and soft, but finely roughened all over. Colour 
greyish-brown. 

Test soft, cartilaginous, not stiff; thin on right side, much thicker on left, 
especially at the area of attachment, where it increases to 1*5 cm. ; smooth and 
glistening on inner surface ; clear and transparent in section. Vessels not con- 
spicuous. 

Mantle. — Shape long and narrow ; siphons long, especially atrial, which is 
placed nearly halfway down the dorsal edge ; musculature strong on right side, 
almost absent on left, where the mantle is thin and membranous; sphincters 
moderately developed. 

Branchial Sac rather delicate and not plicated. Transverse vessels alter- 
nately larger and smaller, the larger ones with broad membranes hanging 
from them. Internal longitudinal bars narrow, bearing large curved papillae 
at the angles of the meshes. Stigmata long and narrow, usually five in each 
mesh. 

Dorsal Lamina narrow, slightly ribbed transversely, and toothed on the 
margin ; double for a short distance at the anterior end. 

Tentacles numerous, of several sizes, some very long (up to 1*5 cm.), stout 
at the base. 

Dorsal Tubercle small, irregularly ovate in outline, aperture anterior, horns 
not coiled. 

Alimentary Canal not large, placed on the left side of the body about the 
middle. (Esophageal aperture two-thirds of the way down the dorsal edge of 
the branchial sac ; stomach irregularly pyriform ; intestine rather wide, and 
forming a narrow loop. 

Genitalia in intestinal loop, Spermatic vesicles extending over the greater 
part of the intestine. Vas deferens wide and prominent, running along the 
posterior and dorsal side of the rectum towards the atrial aperture. 

Three large specimens and one small one of this new species of Ascidia 
were obtained in the second haul of the dredge at Station 13 (31st August 1882, 
in the centre of the " warm area "), from a depth of 570 fathoms, bottom ooze. 
All of the specimens were more or less incrusted, especially upon the left side, 
with fragments of sponges and worm tubes ; one of them had a few specimens 
of a small Tubularian zoophyte adhering, while the smallest individual had 
several specimens of Anomia ephippium attached to its test. 

The largest specimen is 13 5 cm. in length and 8 cm. in breadth, the smallest 
5 cm. in length and 3 cm. in breadth. The remaining two are 9*5 cm. and 
10*5 cm. respectively in length, while both measure 6*5 cm. across at the widest 
point. In general shape, and especially in the position of the atrial aperture 



98 DR W. A. HERDMAN ON 

(see PI. XVI. fig. 1), this species shows resemblances to Ascidia lata* and 
Ascidia meridionalis,f but it differs greatly from both these species in internal 
structure. 

The shape of the body -when the test is removed (PI. XVI. fig. 3) is remark- 
able on account of its great antero-posterior elongation, and the position of the 
stomach and the intestine so far from the posterior end. The appearance 
presented by the body when seen from the left side suggests that this peculiar 
relation is caused by the branchial sac having extended posteriorly beyond the 
stomach. 

The muscular pad at the base of the branchial siphon, from the lower edge 
of which the tentacles spring (PI. XVI. fig. 6), is very strong. The tentacles 
are large, and so numerous that their bases touch. 

The dorsal tubercle (PL XVI. fig. 6) is peculiar, inasmuch as the left horn 
is bifurcated ; however, this is very possibly merely an individual variation. 

With the exception of Ascidia meridionalis, obtained during the " Challenger" 
expedition at 600 fathoms, off the south-eastern coast of South America, the 
present species was found at the greatest depth from which the genus Ascidia 
has been recorded. 



Ascidia virginea, O. P. Muller (PL XVII. figs. 3 and 4). 
( = Ascidia sordida, Alder & Hancock, Cat. Mar. Moll. Northumb., &c.) 

At first sight, and after a hasty examination, I was inclined to consider this 
specimen as a new species, but after a more careful investigation of its anatomy 
I prefer to regard it as merely an abnormally-shaped individual of Ascidia 
virginea. If this form should be found to occur with sufficient frequency it 
might be distinguished as variety pedunculata. I remember dredging a 
similar individual a few years ago in the Firth of Forth, but cannot now 
find the specimen in my collection. 

The body is pyriform, shortly pedunculated, and attached by the posterior 
end (PL XVII. fig. 3) ; it is slightly compressed dorso-ventrally. The anterior 
end is narrow, but widens rapidly, especially on the right side ; the widest point 
is reached at a little more than one-eighth of the distance from the anterior to 
the posterior end. The anterior half is moderately swollen, the posterior 
half is much narrower, and forms a short stalk. The apertures are both near 
the anterior end, not distant, sessile, but conspicuously lobed. The surface 
is rather irregular, but smooth ; it is somewhat incrusted by foreign objects. 
The peduncle is slightly enlarged at its lower extremity to form a disc of 

* HSBDMAN on British Tunicata, Linn. Soc. Jour., ZooL, vol. xv. p. 277. 

t Hhbdman, Report upon the Tunicata of the " Challenger" Expedition, part i. p. 207. 



THE " TRITON " TUNICATA. 99 

attachment. The colour is dirt}' grey. Length, 5 cm. ; greatest breadth, 
2 cm. ; thickness of peduncle, 1 cm. 

The test is thin, except at the top of the peduncle, where it is considerably 
thickened. The peduncle is solid, and formed of test alone. The vascular 
trunks enter the test at the top of the peduncle. 

When the test is removed the body has the appearance usual in Ascidia 
virginea, and the mantle is in a normal condition, strongly muscular on the 
right side, but thin and weak upon the left. 

The branchial sac corresponds in all respects with what I have found in 
other specimens of the species. It is longitudinally plicated to a slight degree, 
has strong internal longitudinal bars with no papillae, and square meshes with 
five or six stigmata each. 

The dorsal lamina is strongly ribbed transversely. The tentacles are 
numerous, closely packed together, and of several sizes. Those of the first 
order are long and slender. The dorsal tubercle is simple, and elongated 
antero-posteriorly. The posterior three-fourths or so is enclosed in the small 
peritubercular area, and the end is pointed. The aperture is anterior, and 
the horns are not coiled (PI. XVII. fig. 4). Ascidia virginea is one of the 
most variable species known, in regard to the shape of the dorsal tubercle. 4 ' 5 ' 
The present form is rather simpler and more symmetrical than usual, and is 
peculiar in having the posterior end pointed. 

The single specimen was trawled off the Butt of Lewis, 25th August 1882, 
depth, 40 fathoms. 

Ciona intestinalis, Linn. (PL XVII. figs. 1 and 2). 

Sixteen specimens of this common British species were in the collection sent 
to me, four of them being preserved in absolute alcohol. They were all obtained 
by the trawl at Station 3 (8th August 1882, at the north-west end of the 
Wyville-Thomson ridge, and north of the " warm area," bottom s. sh.) from 
a depth of 87 fathoms. This is the greatest depth known to me at which this 
species has been found, but it is quite possible that it may have been obtained 
in Scandinavian seas, or in the Mediterranean at greater depths, though I have 
been unable to find records of such instances. The " Triton " specimens are 
all of fair size, and as some of them are much corrugated it is probable that 
they were large individuals when alive and expanded. 

The tests are more colourless than is usual with shallow water specimens 
from our own coasts, and have almost none of that dull green tint which may 
generally be observed even after preservation in spirit. On the other hand, 

* See Herdman, "On the 'Olfactory Tubercle' as a Specific Character in Simple Ascidians," 
Proc. Roy. Pliys. Soc. Edin., vol. vi. session ex. p. 256, 1881. 



100 DR W. A. HERDMAN ON 

the red pigment spots at the branchial and atrial apertures and the pigment on 
the aggregation of glands at the opening of the vas deferens are as bright and 
conspicuous as is usual in the living animal. In one of the specimens preserved 
in absolute alcohol, which was dissected, the inner surface of the test was found 
to be closely ribbed longitudinally and less conspicuously so transversely. This 
has been caused by the test having remained attached to the mantle during the 
contraction of the latter, and having become impressed by the subjacent 
strongly developed longitudinal muscles. 

The papillae at the angles of the meshes in the branchial sac seemed 
larger than is usual in the species, and were certainly much larger than those 
represented by Heller'" from a Mediterranean specimen. In some places 
their length equalled the space between two neighbouring internal longi- 
tudinal bars, so that when laid flat they stretched across the mesh. 

I have observed considerable individual variation in the branchial sac of 
this species. In 188 It I noted a variability in the number of stigmata con- 
tained in each mesh, and since then I have met with several other points in 
which individuals differed. The specimens examined have been from various 
parts of the British seas— the Firth of Forth on the east ; Lamlash Bay, Loch 
Fyne, and the Sound of Mull on the west ; and Poole, Portland, and Dartmouth 
on the south coast. I have also specimens from the Channel Islands, the 
Chausey Archipelago, and the coast of Brittany, in addition to those collected 
by the " Triton " in the North Atlantic. 

I have very rarely seen the arrangement figured by Heller | where the 
meshes are represented as being greatly elongated transversely, and occupied 
by two rows of extremely short stigmata. Usually the meshes are nearly 
square, and are divided into two areas by a delicate transverse membrane, 
which, however, does not generally interrupt the stigmata. This is shown at 
tr' in fig. 2, where the membrane crosses the mesh, while the stigmata extend 
behind. In the mesh below no transverse membrane is present, while 
in fig. 1 three are seen, the central one being much the strongest. This 
last arrangement was found to be very prevalent in the sac of the " Triton " 
specimen examined. In some specimens the meshes, in place of being square, 
are considerably elongated longitudinally — the reverse of the variation figured 
by Heller — and the contained stigmata are very long and narrow. In this 
case the meshes are always divided by from one to three transverse membranes. 

The papilhe upon the internal longitudinal bars appear liable to considerable 
variations in their size and arrangement. In some cases they are present only 
at the angles of the meshes, as shown in the lower part of fig. 2, and are then 
all of much the same size. Where the meshes are divided there is usually a 

* Untersuchungen ilber die Tunicaten des adriatischen Meeres, Abth. ii. Taf. iv. fig. 6, Wien, 1875. 
t Jour. Linn. Soc, Zool, vol. xv. p. 332. X Loc. cit. 



THE "TRITON TUNICATA. 101 

papilla placed at each point of intersection with the median or chief trans- 
verse membrane (tr' in the figs.) and the internal longitudinal bars. These 
papillae are usually rather smaller than those at the angles of the meshes, 
but in some cases (as is shown in the upper part of fig. 2) the papillae may be 
all of the same size. I have found the chief papillae varying in size from a little 
less than one-half* the breadth of the mesh to (in the case of the "Triton" 
specimen) the entire breadth. In fig. 1 the papillae have been omitted, in 
order that the transverse membranes might be clearly seen. 

Returning to the " Triton " specimen, the margin of the anus was expanded 
and more deeply indented than is shown in Heller's figure. t The oviduct was 
found full of ova, some of which were also discovered in the peribranchial 
cavity ; and the pigmented glands at the aperture of the vas deferens seemed to 
form a larger and more conspicuous mass than usual. 

Order II.— THALIACEA. 

Both families of this order, the Doliolidae and the Salpidae, are represented 
in the collection. 

Family I. — Doliolidae. 

Doliolum denticulatum, Quoyand Gaimard (Pis. XVIII., XIX., and XX.). 

The five or six thousand specimens of Doliolum in the collection are, I was 
astonished to find, all one form, and this I have identified with the sexual 
generation of Doliolum denticulatum.^ This species was first described and 
figured by Quoy and Gaimard, the founders of the genus, in the zoology of 
the voyage of the " Astrolabe,"§ in 1835. It had been found in the Malay 
Archipelago near the islands of Amboyna and Vanikoro. Sixteen years later 
Huxley |] published his observations made upon certain Tunicata during the 
voyage of the "Rattlesnake." In this paper very considerable additions are 
made to the knowledge of the structure of Doliolum, and the relations in 

* In Heller's figure they are about one-fourth, of the breadth of the rnesh. 

t hoc. tit., Taf. v. fig. 8. 

% As will be pointed out in the following description, there are a "number of details, especially in 
the branchial sac, in which these " Triton " specimens differ from the accounts of Doliolum denticula- 
tum given, by Keferstein and Ehlers (Zoologische Beitrcige, 1861) and by Grobben (Arbeiten aus 
dem. Zoolog. Instlt. der Univ. Wien, 1882). As, however, they agree with those authors' descriptions 
in the more important anatomical features, and as they could not be referred to any other known 
species, I prefer to consider them as a variety of Doliolum denticulatum. It is improbable that they are 
an undescribed species, since they are apparently so common in the North Atlantic. Doliolum den- 
ticulatum is probably rather a variable form. 

§ "Voyage de cUcouvertes de 1' Astrolabe," Zoologie, T. iii. pt. 2, p. 599; Atlas, Mollusques, 
pi. lxxxix. figs. 25-28. Paris, 1835. 

|| "Eemarks upon Appendicularia and Doliolium," &c, Phil. Trans, for 1851, part 2, p. 599, pi. 
xviii. 

VOL. XXXII. PART I. S 



102 DR W. A. HEKDMAN ON 

which the genus stands to Salpa and Pyrosoma are pointed out. Huxley's 
specimens had been obtained in the South Pacific between Australia and New 
Zealand. During the next few years Krohn,* Gegenbaur^ and Leuckart^: 
worked at the Pelagic Tunicata, but their efforts, and especially those of the 
two former investigators, were mainly directed towards the elucidation of the 
remarkably complex life-history of Doliolum, and the additions made to the 
knowledge of the adult structure were comparatively few and unimportant. 

Keferstein and Ehlers, § during the winter of 1859-60, investigated several 
Mediterranean forms of Doliolum, both as regards their anatomy and life- 
history. As the chief subject of their observations was Doliolum denticulatum , 
it has been of great advantage to have their description and careful figures 
with which to compare the "Triton" specimens. No works of importance 
upon Doliolum have appeared since, with the exception of Ulianin's || and 
Grobben's^ papers, published during the last two years. These are mainly 
devoted to the development and life-history, which is now almost completely 
cleared up. Grobben, however, treats also of the anatomy and histology, and 
to his memoir, as well as to that of Keferstein and Ehlers, I shall have to 
refer in the following description. 

Commencing with the body form, most of the "Triton" specimens are of 
the characteristic barrel shape (see PI. XVIII. figs. 1, 2, 3, 4, and 9), some of 
them (as fig. 9, which was drawn from a specimen obtained August 4-5 from 
12 fathoms) being rather wider than others. Some specimens, however (see fig. 
10, which represents two specimens obtained on August 5th from a depth of 530 
fathoms), are very different in shape, being narrow, elongated, and almost 
cylindrical. At first I separated out a number of these forms, under the 
impression that they were a distinct species from the barrel-shaped individuals, 
but found afterwards, when examining their structure, that the two kinds 
agreed perfectly in all the details of their anatomy. Since then I have found 
various intermediate shapes between those shown in figs. 9 and 10, and have 
consequently no hesitation in considering them all as one species. As a rule, I 
find it is the specimens from considerable depths, and those which have been 
closely packed in a tube or bottle, which diverge most from the typical barrel 

* " TJeber die Gattung Doliolum," &c, Archiv fur Naturgeschichte, 1852, p. 53. 

t " Ueber die Entwieklung von Doliolum," Zeitsehrift fur wissensch., Zoologie, 1853, Bd. v. p. 13; 
and "Ueber die Entwicklungscyclus von Doliolum," &c, Zeitschrift fur wissensch., Zoologie, 1855, 
Bd. vii. p. 283. 

% Zoologische Untersuchungen, Heft ii., " Salpen und Vcrwandte," Giessen, 1854. 

§ Zoologische Beitrdge,m., "Ueber dieAnatomie und Entwickclung von Doliolum," Leipzig, 1861. 

|| " TJeber die embryonale Entwieklung des Doliolum," Zoologischer Anzeiger, iv. No. 92, p. 
472, and No. 96, p. 575, 1881; also " Zur Naturgeschichte des Doliolum," Zoologischer Anzeiger, v. 
p. 429 and p. 447, 1882. 

IT "Doliolum und sein Generationswechsel," &c, Arheiten aus dem Zoolog. Instit. der Univ. 
Wien, &c, t. iv. h. 2, 1882. 



THE "TRITON" TUNTCATA. 103 

shape, hence it is probable that the abnormal form is clue either to the 
animal not having been killed suddenly enough or to imperfect preservation. 
All of the " Triton " specimens, with the exception of the five small ones 
mentioned in the list on page 93, are between 6 mm. and 12 mm. in length, 
and most of them measure 1 cm. This size is apparently much greater than 
that of Mediterranean specimens, as Grobben speaks of his as being about 
2 o mm., while Keferstein and Ehlers figure one 3 mm. in length. 

Most of the specimens are in ordinary rectified spirit, while a few have been 
treated in each of the following methods : — 

1. Preserved in absolute alcohol. 

2. Put first into chromic acid solution and then into absolute alcohol. 

3. Preserved in a saturated solution of picric acid. 

4. Put first into solution of osmic acid and then into absolute alcohol. 

5. Put first into solution of picric acid and then into absolute alcohol. 

6. Preserved in solution of chromic acid. 

These specimens were all in excellent condition for examination, and the 
different methods appear to give almost equally good results. Perhaps the best 
preparations for most histological points were obtained from the specimens 
preserved in chromic acid by thoroughly washing in alcohol, staining in picro- 
carmine, and mounting in Farra.nt's solution ; while for some few special 
points the specimens preserved in osmic acid solution and absolute alcohol 
excelled. 

The test is almost absent, being represented merely by a delicate structure- 
less layer over the ectoderm, which covers the surface of the mantle. The 
mantle contains the muscular bands or hoops, which, in this form, are eight 
in number (m 1 to m 8 in the figs.). The first and last of these bands form 
sphincters for the apertures, and usually appear to terminate the body anteriorly 
and posteriorly, as shown in Plate XVIII. fig. 4, the delicate denticulated 
margins of the branchial and atrial apertures being almost invariably turned 
in or directed across the opening. This denticulated margin was turned out 
in the chromic acid specimens examined, and was more perfectly preserved 
than in any of the others. It is divided into twelve lobes around the branchial 
aperture and ten around the atrial. The muscle bands are composed of very 
long non-striped fibres, closely and regularly placed, as shown in Plate XVIII. 
fig. 6. Sometimes, as in fig. 5 (from a picric acid specimen), the fibres are 
thrown into undulations. 

The wide branchial aperture leads into the branchial siphon, which, as there 
is no diaphragm and no circlet of tentacles, may be considered as extending back 
to the peripharyngeal band. This band, in all the specimens which I have 
examined, runs in most of its course between the 2nd and 3rd muscle bands, or 
in the 2nd intermuscular space (PL XVIII. fig. 11, p.p), and marks the anterior 



104 DR W. A. HERDMAN ON 

end of the branchial sac, which extends back usually to between the 5th and 
6th muscle bands. Grobben, however, describes and figures* the peripharyngeal 
band as lying in the 1st intermuscular space. Keferstein and Ehlers also 
represent t the branchial sac as extending anteriorly into the 1st intermuscular 
space, an arrangement which I have been unable to find in the "Triton" 
specimens. 

The arrangement of the stigmata is as follows : — A series commences on 
each side of the median dorsal line, close behind the 3rd muscle band (see 
PL XVIII. figs. 8 and 11, sg), and extends posteriorly for a variable distance 
— usually to about the 6th muscle band. The stigmata in this series differ 
greatly in size among themselves. The most anterior one is very short — in 
fact, almost circular. The next three or four increase rapidly in length till 
the level of the nerve ganglion (n.g.) is reached, and then the increase becomes 
less marked. Towards the posterior end there is a slight diminution in size. 
Considered as a whole, the two series of stigmata diverge somewhat posteriorly, 
so that the space between them in the dorsal middle line is narrow in the 3rd 
intermuscular space, the region of the ganglion, but widens posteriorly (PI. 
XVIII. fig. 11). As a result of this arrangement, when the branchial sac is 
seen from the side, the dorsal series of stigmata appear to slope downwards and 
backwards from the region of the ganglion (see PI. XVIII. fig. 4). There is also 
a series of stigmata upon each side of the ventral median line. These, how- 
ever, do not extend so far anteriorly as the dorsal series do. They commence 
behind the 4th muscle band, near the posterior extremity of the endostyle, 
and extend backwards, increasing in length rapidly at first, and then maintain 
ing their size till they come to the sides of the oesophageal aperture. Here 
they commence to curve dorsally, and then towards each other, finally uniting 
in the dorsal middle line, usually near the 6th muscle band, so as to form a curve 
surrounding the membranous area in which the oesophageal aperture is placed 
(see PI. XIX. fig. 10, sg). 

The membranous side wall of the branchial sac is very wide anteriorly, 
where it extends from the endostyle almost to the ganglion dorsally. In the 
4th intermuscular space it is encroached upon by the development of the 
ventral series of stigmata, and as it is traced posteriorly from this point, it 
becomes narrower and narrower, till finally it merges upon each side into the 
median dorsal area through the failure of the dorsal stigmata. The exact 
number of stigmata in the different series varies of course according to the 
size of the individual. In mature specimens there are usually from thirty 
to fifty in the dorsal row on each side, and about thirty as an average in each 
ventral series. 

* Loc. cit, p. 13, woodcut, and pi. i. fig. 1, wh. 
f Zoologische Beitrtiga, pi. ix. figs. 1 and 2. 



THE " TRITON " TUNICATA. 105 

A glance at Plate IX. of Keferstein and Ehlers' work suggests that the 
specimens there figured may have been young, and the number of stigmata 
shown (thirteen to fifteen in the dorsal row) is just about the number present 
in the smallest " Triton " specimens (2 mm. long). Perhaps this may also 
account for the great anterior extension of the dorsal rows of stigmata which 
are represented as reaching in front of the 2nd muscle band, while in the 
" Triton" specimens they were never seen in front of the 3rd (see PI. XVIII. 
figs. 8 and 11). The ventral band, containing fifteen stigmata, is shown by 
Keferstein and Ehlers extending to the front of the 3rd intermuscular 
space, while in all the specimens which I have examined, it has terminated 
some place in the 4th intermuscular space. Grobben"* speaks of forty-two as 
the largest number of stigmata upon each side which he observed, Keferstein 
and Ehlers t say that the number may vary from twenty-six to forty-three, 
while the usual number in the " Triton " specimens was about seventy ! 
Grobben also describes and figures J the series of stigmata as extending exactly 
one intermuscular space further anteriorly than I found to be the case. As 
they appear always to terminate posteriorly in the neighbourhood of the 6th 
muscle band, it is obvious that there must be a greater number of stigmata in 
each intermuscular space in the " Triton " specimens than in those from the 
Mediterranean, and a comparison of my figures on theone hand, with those of 
Grobben and of Keferstein and Ehlers on the other, shows that this is the 
case. 

The bars separating the stigmata are covered in the usual manner with 
ciliated cells placed in such a position that the cilia project across the 
stigmata. These cells are not placed in a single row, as a surface view of the 
branchial sac such as that shown in fig. 2, Plate XIX. might lead one to 
imagine, but are placed in groups of four or five elongated cells placed closely 
side by side § (see PI. XIX. fig. 3). This arrangement can only be made out 
by viewing the bar upon which the cells are placed from the interior of the 
stigma. An osmic acid preparation showed with a Zeiss x^-in. oil immersion 
objective that these cells were nucleated and nucleolated, and had a striated 
band upon the free edge, from which the cilia project (PI. XIX. fig. 4). At the 
rounded ends of the stigmata the ciliated cells are very numerous, forming 
many rows. They also change their character (see PI. XIX. fig. 2), and become 
cubical, spherical, or polygonal in shape. 

The endostyle is always a well-marked feature in the ventral middle line 
of the branchial sac. It extends from midway between the 2nd and 3rd 
muscle bands anteriorly (PI. XVIII. figs. 7 and 11, en) to somewhere in the 

* Loc. cit, p. 16. f Loc. cit, p. 57. J Loc. cit., p. 16, and pi. i. fig. 1. 

§ Grobben has figured a similar arrangement in the case of the asexual forms of the same species 
(Loc. cit., pi. v. figs. 34, &c). 



106 DPv W. A. HERD MAN ON 

4th intermuscular space posteriorly. Keferstein and Ehlers represent it as 
extending rather further anteriorly, but terminating at the 4th muscle band 
posteriorly ; while in Grobben's figures it commences as in mine, but terminates 
in the 3rd intermuscular space. At its anterior extremity the endostyle is 
joined by the ventral ends of the two peripharyngeal bands (see PI. XVIII. 
figs. 7 and 11), while posteriorly it is continued into a membrane with a free 
projecting edge which runs backwards over the heart, and then round the left 
hand side of the oesophageal aperture (PI. XIX. fig. 10, mb). The histology of 
the endostyle has been minutely described by Grobben (loc. cit.). 

The prebranchial zone, the region anterior to the peripharyngeal band, is 
covered by squamous epithelium. In osmic acid preparations the protoplasm 
in these cells is found to have become contracted and aggregated around the 
distinct nuclei, so as to present the appearance, shown in Plate XIX. fig. 6, 
of stellate cells united by their processes to form a network. 

On- the surface of the peripharyngeal band this epithelium has become 
modified into long fusiform cells (PI. XIX. fig. 5) all placed with their long axes 
directed along the band. When not so highly magnified, or not stained 
properly, they give rise to the appearance shown in Plate XVIII. fig. 13. The 
dorsal ends of the two peripharyngeal bands meet, but at this point they are 
twisted round so as to form a double spiral towards the right, the left hand 
band performing one and a half turns, and the right a single turn only. This 
arrangement is shown in figs. 8, 11, and 12 on Plate XVIIL, and at once 
suggests the form of the dorsal tubercle found in a similar position in the 
Ascidiacea. That organ is represented, however, in Doliolum, not by the curved 
dorsal part of the peripharyngeal band which has been described, but by the 
anterior end of the deeply funnel-shaped depression indicated by n.a in figs. 8 
and 12.* 

The part of the prebranchial zone which is enclosed by the dorsal spirals of 
the peripharyngeal band has its epithelium modified into large polygonal cells, 
the outlines and nuclei of which are strongly marked. In the preparation from 
which fig. 7 on Plate XIX. was drawn, the protoplasm in most of the 
cells was aggregated around the nucleus in a stellate form. 

The nerve ganglion is placed in the mantle, and indicates the median dorsal 
line. It is small, but very distinct from its opacity. It is usually rudely cubical 
or nearly spherical in shape, and gives off four large nerve trunks, two at its 
anterior and two at its posterior angles, besides smaller nerves between. It 
usually lies a short distance behind the 3rd muscle band, as shown in figs. 8 

* Possibly the cavity {n.a in the figures) represents merely the opening of the duct from the 
neural gland into the dorsal tubercle of the Ascidiacea, while the spirals {d.t, in PI. XVIIL fig. 11) 
indicate the sense-organ, which I believe the dorsal tubercle to have formerly been (see Proc. Roy. 
Soc. Edin,, p. 144, 1882-83. 



THE "TRITON" TXJNICATA. 107 

and 11 on Plate XVIII., but may be further back as represented by Keferstein 
and Ehlers in their pi. ix. fig. 1. It may advance forward, so as to touch 
the 3rd muscle band (see PI. XIX. fig. 1), but is never found outside the 3rd 
intermuscular space. 

The ganglion is very opaque, and it is difficult to make out its constitution. 
Fig. 8 on Plate XTX. shows its anterior end with four nerves, two large and 
two small, arising from it. Grobben * has apparently not noticed the smaller 
pair (PI. XIX. fig. 8, n'), but he describes a median anterior nerve which I could 
not find in any of my specimens, unless it be the nerve shown at n in Plate 

XVIII. fig. 12, which is drawn from an individual having apparently only 
three anterior nerves. As in other Tunicates, where the matter has been 
investigated, the nerve cells are all in the outer layers of the ganglion, and the 
centre is formed of a mass of delicate interlacing fibres and granular matter. 
Fig. 12, Plate XIX., shows this arrangement well. The nerve cells are 
ovate, unipolar, bipolar, or multipolar, rarely the latter. They are finely 
granular, and have distinct nuclei and nucleoli (see PI. XIX. fig. 13). 

On the ventral surface of the ganglion there lies a dark mass which must be 
the neural gland, but of which I was unable to make out the structure definitely. 
It gives rise anteriorly to a very delicate duct which runs directly forwards to 
open at the prebranchial zone into the funnel-shaped depression mentioned 
above (see PI. XVIII. figs. 8 and 12). This duct is wide where it emerges from 
below the ganglion, and its wall is formed of distinct polygonal cells (see PL 

XIX. fig. 8 n.d). It rapidly narrows, however, as it runs forwards, and the 
cell elements lose their distinctness, so that in the part immediately in front 
of the 3rd muscle band (PL XVIII. fig. 8, n.d) it is very difficult to make 
out any structure in the wall. In front of this point it again becomes more 
distinct, and the cells vary from fusiform to squamous in their character (PL 
XIX. fig. 9, n.d) up to the point where the duct joins the funnel-shaped de- 
pression. 

The length of this neural duct varies with the positions of the ganglion and 
of the aperture in the prebranchial zone. The normal arrangement is shown in 
figs. 8 and 11, Plate XVIII., while in fig. 1, Plate XIX., it is abnormally 
short, on account of the unusual position of the ganglion. The aperture 
in the prebranchial zone is always placed in the median dorsal line upon the 
most anterior point of the spirals formed by the peripharyngeal band, and 
therefore in the 2nd intermuscular space. Grobben and also Keferstein and 
Ehlers figure it in the 1st intermuscular space, an arrangement which I have 
never seen. Although the peripharyngeal bands encroach upon the 1st inter- 
muscular space at the two sides (see PL XVIII. fig. 11), they always, in the 
specimens which I have examined, dip posteriorly at the ventral and dorsal 

* Loe. tit., p. 9. 



108 DE W. A. HEEDMAN ON 

ends, and hence the anterior end of the endostyle and the dorsal spirals come 
to be situated in the 2nd intermuscular space. 

The aperture in the prebranchial zone is small, and leads into a funnel- 
shaped cavity continuous with the neural duct (PI. XIX. fig. 9). At the posterior 
narrower end of this cavity, the flat cells lining the duct become gradually 
cubical and then low columnar, and bear each a long cilium which projects into 
the centre of the cavity, and is directed posteriorly. This funnel-shaped 
cavity is apparently merely the aperture of the neural duct. I have searched in 
vain for any trace of a sensory apparatus. In several specimens I have suc- 
ceeded in tracing one of the smaller nerves given off from the anterior end 
of the ganglion in its entire course forwards (see PI. XVIII. fig. 12, n). It 
runs alongside the duct and close to it, but passes the funnel-shaped cavity 
upon its left side without giving off any branch, and continues its way 
anteriorly to supply the lobes around the branchial aperture. 

The heart is situated on the ventral surface of the posterior end of the 
branchial sac, just between the termination of the endostyle and the oesopha- 
geal aperture and in the posterior part of the 4th intermuscular space 
(PI. XIX. fig. 10, h). In chromic acid specimens the transverse muscle bands 
of the wall of the heart were well shown (see PI. XIX. fig. 11), but each band 
appears to me to be composed of a large number of very fine fibres placed side 
by side, and not of one fibre only as supposed by Keferstein and Ehlers.* 

The alimentary canal, omitting the pharynx or branchial sac, which has 
been already considered, consists of oesophagus, stomach, and intestine, and 
forms a curved tube, lying mainly in the 5th and 6th intermuscular spaces 
(PI. XVIII. fig. 4). 

The oesophageal aperture is placed at the posterior end of the branchial sac 
in the middle line, and nearer to the ventral than to the dorsal surface. It 
lies in the membranous area prolonged back from the region around the 
posterior extremity of the endostyle (PI. XIX. fig. 10), and is surrounded 
laterally and dorsally by the posterior end of the ventral series of stigmata. 
This is a notable point, since it is usual in the Ascidiacea for the oesophageal 
aperture to be placed on the dorsal edge of the sac, and invariably so amongst 
Ascidiae Simplices, in some of which it is placed nearer to the anterior than 
to the posterior end of the dorsal edge. 

The oesophageal aperture is surrounded by a membranous rim, which on its 
left anterior edge is continued forwards to join the posterior extremity of the 
endostyle, while at its other end, after surrounding the aperture (see PL XIX. 
fig. 10, mb), it is continued as a spiral ridge into the cavity of the oesophagus. 
The oesophagus is short, and leads downwards and backwards to the anterior 
end of the large irregularly quadrangular stomach (PL XX. fig. 1, st). From 

* Loc. cit., p. 58. 



THE "TRITON" TUNICATA. 109 

the posterior end of this the short curved intestine emerges. The stomach 
lies in the 5th intermuscular space, and the intestine runs backwards till it 
almost or quite reaches the 7th muscle band, and then turns dorsally and to 
the right, and finally runs forwards to terminate in the anus placed in the 5th 
intermuscular space, over the stomach (PL XVIII. fig. 4). According to 
Keferstein and Ehlers the anus is situated at the posterior part of the 5th in- 
termuscular space, or upon the sixth muscle band, while according to Grobben 
it lies in the 6th intermuscular space. Huxley figures it in the fifth inter- 
muscular space. The epithelium lining the intestine is polygonal in surface 
view (PL XX. fig. 4) and very distinctly nucleated. In the wall of the stomach 
the cells are columnar and more darkly coloured. 

Two glandular systems, which seem to be quite distinct, are found in 
connection with this alimentary canal. First, along the ventral surface of the 
stomach, especially towards the pyloric end, and more or less scattered over 
the first portion of the intestine, may be found masses of rather darkly coloured 
glandular-looking caeca (see PL XX. fig. 1, gT). These branch and apparently 
anastomose occasionally, forming rude networks, but the branches are short 
and stout, and the meshes small and irregular. No duct or opening into the 
alimentary canal was visible. With a higher magnification the cseca present 
somewhat the appearance shown in Plate XX. fig. 5 — masses of cells rounded 
or polygonal in outline, but rarely angular, having small indistinct nuclei and 
granular cell-contents. These clumps of branched cseca have apparently not 
been noticed previously, as I find nothing in the published descriptions and 
figures which could represent them. 

The second glandular apparatus is the system of fine clear-walled tubules 
ramifying over the intestine, which was first pointed out in Doliolum by 
Huxley,* and has since been more or less completely described by Leuckart, 
Gegenbaur, Keferstein and Ehlers, and Grobben. It has also been recently 
investigated by CHANDELONt in Perophora and Salpa, where it has very much 
the same arrangement as in Doliolum. Chandelon comes to the conclusion 
that the system can be compared neither with a kidney nor a liver, but 
that it is probably a digestive gland of some kind. 

In the specimens which I examined this system appeared generally well 
i developed, although it was sometimes difficult to make out, owing to the 
opacity of the alimentary canal caused by its food contents. In Plate XX. 
fig. 1, d indicates the duct of this system, which is a clear- walled, almost 
transparent vessel, entering the pyloric end of the stomach. From this point 
it may be traced upwards and backwards (PL XX. fig 1, represents a specimen 

* Phil Trans., 1851. 

t "Recherches sur une annexe de tube digestif des Tuniciers," Bulletins de I'Academie Royale de 
Belgique, 2 me ser. t. xxxix. No. 6, 1875. 

VOL. XXXII. PART I. T 



110 DK W. A. HERDMAN ON 

in which the intestine lias been turned ventrally so as to expose the whole 
alimentary system) to about the middle of the intestine. At this point the 
duct divides, and its two branches run over the wall of the intestine, subdivid- 
ing as they go. The twigs branch freely and sometimes anastomose (PI. XX. 
fig. 3). Many of them end in short caecal projections, and in some cases these 
are enlarged to form terminal knobs (see PI. XX. fig. 3, c), which may contain 
irregularly rounded bright bodies (concretions ?) similar to those described by 
Chandelon in Perophora. 

The wall of the main duct is lined by regularly arranged fusiform cells 
placed with their long axes parallel to the length of the duct (PI. XX. fig. 2). 
The tubules on the intestine are lined by flattened epithelium bulging into the 
lumen where the nuclei occur, and enlarged into cubical cells in the terminal 
knobs. 

The apertures of the reproductive organs lie at the posterior end of the 
body behind the alimentary canal, and usually in the 6th intermuscular space. 
All the " Triton " specimens of Doliolum denticulatum examined belong to the 
sexual generation, Keferstein and Ehlers' "generation A," and have both 
male and female organs well developed. 

The ovary is an ovate mass placed usually in front of the 7th muscle band 
(PI. XX. fig. 7, ov), but occasionally behind it (PI. XX. fig. 6, ov). Ova of 
different sizes were almost always distinctly visible in it (PI. XX. fig. 1, g, and 
fig. 13, ov). It opens on its dorsal edge into the atrial cavity. 

The testis, as Huxley * first correctly described, is in the form of a greatly 
elongated tube, usually nearly as long as the body, terminating posteriorly on 
the anterior face of the ovary, and extending forwards for a variable distance 
with rather an irregular course (PI. XX. figs. 6 , 7, &c, and PI. XVIII. figs. 1-4). 
At its posterior end, where it abuts against the ovary, it turns dorsally, 
forming a tube which may be called the vas deferens, and opens into the atrial 
cavity (PI. XX. figs. 13 and U, v.d.). 

The anterior end of the testis is very variable. Keferstein and Ehlers 
state that it may terminate any place between the 3rd and the 1st inter- 
muscular space, and they figure it at the posterior end of the 3rd in one case 
and the anterior end of the 4th in another. Grobben states that it extends 
forward to the 4th muscle band, while Huxley figures it as reaching nearly to 
the 1st. In most of the specimens which I have examined the anterior end is 
placed close to the 2nd muscle band, as shown in Plate XX. figs. 6 and 9. No 
previous investigators, so far as I am aware, either describe or figure the extra- 
ordinary variability in form of this anterior end of the testis. A glance at 
figs. 6, 7, 8, 9, 10, and 11 on Plate XX. shows the extent of this variability. 
In fig. the tube becomes rapidly smaller opposite the 3rd muscle band, 

* Phil. Trans., 1851, part ii. \>. 602. 



THE "TRITON" TUNICATA. Ill 

and, after a short undulating course as a very fine tubule, enlarges into a 
pear-shaped dilatation extending to the 2nd muscle band. In fig. 9, which 
is drawn on a larger scale, there are two dilatations on the narrow part of the 
tube, while in fig. 11 the narrow part is long and convoluted, and extends 
forward to the 2nd muscle band. In fig. 10 the testis reaches the 2nd 
muscle band without any diminution in its calibre, and then, narrowing slightly, 
forms a loop extending almost to the 1st band, after which it curves back to 
wards the 2nd, and ends in a narrow filament. The two remaining cases figured 
are the most remarkable of all. In fig. 8 the tube narrows rapidly opposite 
the 3rd muscle band, and from this point forwards almost to the 1st it remains 
very narrow, but with two large ovate dilatations and several smaller ones upon 
its course. Fig. 7 shows a case where the wider tube extends to the 2nd 
band and then suddenly narrows, but the fine tubule, in place of running 
forwards, turns posteriorly, and eventually reaches the 4th muscle band after 
passing through several irregular dilatations. Throughout, this male system 
was filled with minute granular cells (PI. XX. fig. 12), but no distinct sper- 
matozoa could be made out. 

The most remarkable feature of this " Triton " collection of Doliolidoe is, that 
such vast numbers should prove to be entirely one generation of the same 
species, and all, with a very few exceptions, of much the same size. Questions 
naturally arise such as, Where have they come from ? Where are the asexual 
forms from which they have been produced % and Why are such quantities of 
that species found in that locality at that time ? We are not yet in a position 
to answer any of these questions fully. Mr Murray tells me that when 
captured, they were all drifting from the south-west to the north-east. This 
would carry them from the " warm area " across the " Wyville-Thomson " ridge 
into the " cold area," but what part of the Atlantic they came from, or how far 
north they are carried, is not known. Mr Murray states that "they were 
abundant during the whole time of the cruise, except when we touched upon 
the Faroe bank water." As far as I can judge from the numbers of specimens 
in the tubes collected on the different days, the configuration of the bottom 
and the division of the region explored into " warm " and " cold " areas has 
no effect whatever upon the abundance of the Doliolidse. There are large 
quantities of specimens in the collection from the 3rd to the 5th August, 
halfway between Kona Island and the south-east end of the ridge ; on the 29th 
August, over the centre of the ridge ; on the 28th and 31st August, in the 
" warm area ; " and on 20th to 23rd August, in the " cold area." The region 
from which the smallest numbers have been brought back are those explored 
on the 7th to the 9th August at the north-west extremity of the ridge. 

Mr Murray has kindly supplied me with the following extracts from his 



112 DR \V. A. HERDMAN ON 

journal, which bear upon the abundance of the Doliolida? at different times, and 
relatively to other surface forms : — 

"August 5, 1882. — Doliolums were quite as abundant to-day as yesterday; 
they appeared to be chiefly about 10 fathoms beneath the surface. Diatoms 
in the stomach as usual. The immense mass of these in this portion of the sea 
at this time is very astonishing. 

" The last year (1880), in the " Knight Errant," the most characteristic 
thing in the surface gatherings was the enormous multitude of Acanthometrse, 
and now these are almost absent. 

"August 7. — There was quite a change this morning in reference to the 
general character of the tow-net gatherings. The Doliolums had quite dis- 
appeared, and Acanthometra? were now very abundant, and the most charac- 
teristic animals. 

" In the afternoon, after we had moved south from the Faroe Bank, we got 
again tjie same surface animals as yesterday and the day before, viz., vast 
numbers of Doliolums, some Medusae, larva? of Medusa? or other Coelenterates 
and Copepods. 

" This is a somewhat remarkable change, and would perhaps indicate a 
current of water from a different source than the more northern water of this 
morning. 

" August 18. — The Doliolums also were observed to be phosphorescent, 
emitting electric-like discharges which were divided like forked-lightning, and 
appeared to me to follow the direction of the nervous cords or filaments .... 
Doliolums and Actinia? were again abundant throughout the day, sometimes in 
enormous abundance. 

" August 24. — There are no Doliolums, and only a few Arachnactis in the 

nets this morning, from about 30 or 40 fathoms Doliolums were got in 

some hauls at a depth. of 10 fathoms during the day. 

" August 29. — There were a large number of Doliolums on the surface 
during the day, indeed they masked all the other things in most of the hauls. 
In general, the Doliolums were most abundant about 5 or 6 fathoms beneath 
the surface. 

" August 30. — During the day, in the tow-nets at and near the surface, 
Doliolums and Arachnactis were most abundant, filling the nets each time. 

" It is remarkable that in the tow-nets, at the weights, there were not over 
one or two Doliolums, but many Copepods, apparently Arctic forms, &c. 

' In summary, Doliolums most abundant, masking all the other things for 
weeks. At times the Doliolums appeared to be in vast banks, where they 
were very numerous ; between these banks there were always a few 
stragglers. J. M." 



THE " TRITON " TUNICATA. 113 

Family II. — Salpid^e. 

During the "Triton" expedition only two specimens of Salpa were obtained, 
but curiously enough these show the two conditions — solitary and aggregated 
— of the same species, Salpa runcinata. In August 1880, during the cruise of 
the "Knight Errant" in the same neighbourhood, some large specimens of 
Salpa zonaria were the only Tunicata captured. 

Salpa runcinata, Chamisso. 

1. Solitary form. One specimen, measuring 2-2 cm. in length, was obtained 
on the surface on the 18th August 1882. 

2. Aggregated form. A single member of a chain was captured in the 
tow-net at a depth of 12 fathoms, 4th-5th August 1882. 

This is the Salpa fusi/ormis of Cuvier, and has the body prolonged both 
anteriorly and posteriorly beyond the branchial and atrial apertures into long 
tapering appendages. The body proper measures 15 cm. in length and 1 cm. 
in breadth, while the anterior appendage extends beyond the branchial aper- 
ture for 1-4 cm., and the posterior appendage beyond the atrial aperture for 
1*7 cm. 

Salpa runcinata is a well known Scandinavian form, and has been obtained 
in British seas before now. Early in the present century, Dr John Macculloch 
described ( Western Isles* vol. ii. p. 187) and figured, under the name of 
Salpa moniliformis, a form which may have been the aggregate condition of S. 
runcinata. He found the chains occurring in abundance in autumn in the 
harbours of Canna and Campbellton. In the spring of 1821 Dr Fleming found 
many chains a foot and more in length upon the Caithness coast ; and about 
thirty years later Professor Edward Forbes identified with Salpa runcinata, 
both solitary and aggregated, some specimens captured by Lieutenant Thomas, 
E.N., in the Orkney Seas. In 1868 Professor M'LsrrosHt came upon vast quan- 
tities of both the solitary and the chain form of Salpa runcinata upon the east 
shores of North Uist, in company with both forms of Salpa spinosa, Otto, a 
species which Forbes had predicted would probably be found in the Hebrides. 

Salpa zonaria, Chamisso. 

Ten specimens of this form were obtained in the tow-net, at a depth of 20 
fathoms, on 10th August 1880, during the cruise of the " KnightErrant." The 
specimens are well preserved, and are all about 4 cm. in length. 

* See Forbes and Hanley, History of the British Mollusca, vol. i. p. 50, 1853. 
f See Jour. Linn. Soc, ZooL, vol. ix. p. 41. 



114 DR W. A. HERDMAN ON 

Postscript. 

Since the above was written, I have received from Mr Murray another 
"Triton" specimen. This necessitates the following addition to my report 
which should be inserted between " Ascidiacea" and " Family Cynthiidse," near 
the top of page 95 : — 

Family Molgulid^e. 

Eugyra glutinans, Moller. 

A single specimen of this widely distributed species was obtained in the 
second haul of the trawl on the 22nd August 1882, at Station 8 (in the " cold 
area," near the S.E. end of the " Wyville-Thomson " ridge), from a depth of 640 
fathoms. This is a greater depth than any from which Molgulidae were 
obtained during the " Challenger " Expedition. 

The incrusting sand is very fine, and the bare area around the apertures is 
conspicuous. In the branchial sac there are usually about eight coils in the 
spiral forming each infundibulum. The specimen measures 9 mm. in breadth 
by 6 "5 mm. in length. 



EXPLANATION OF THE PLATES. 

The objectives employed while drawing the figures were as follows : — 
Swift, 1 inch — magnifies about 45 diameters. 



» i » 


» 


225 


» 6 » 


)9 


300 


Hartnach, No. 4 


9> 


50 


5 


» 


180 


7 


)) 


330 


Zeiss j 1 ^ oil immersion 


» 


950 



The following system of lettering has been adhered to in all the figures 
at, atrial aperture. 
br, branchial aperture. 
br.f, fold in branchial sac. 

c, enlarged end of tubule of intestinal gland. 

d, duct of intestinal gland 
cU, dorsal lamina. 

d.t, dorsal tubercle. 

en, endostyle. 

g, genital mass. 

gl, gland at pylorus of stomach. 

g.c, nerve cells in outer part of ganglion. 

h, heart. 



THE "TRITON" TUNIC AT A. 115 

h.m, horizontal membrane of branchial sac. 

i, intestine. 

i.l, internal longitudinal bar of branchial sac. 

1, lobe at branchial aperture. 

l.v, fine longitudinal vessel of branchial sac. 

m 1 to ??i 8 , the muscle bands in Doliolum. 

mb, membrane. 

m.b, muscular bundle. 

mh, mesh of branchial sac. 

7i, vf, nerves. 

n.a, aperture of duct from neural gland. 

n.d, duct from neural gland. 

n.g, nerve ganglion. 

02, oesophagus. 

ce.a, oesophageal aperture. 

ov, ovary. 

p, papilla ; p', smaller intermediate papilla. 

p.p, peripharyngeal band. 

sg, stigmata. 

st, stomach. 

t, testis ; t ', anterior prolongation of testis. 

tn, tn', tn", tentacles of 1st, 2nd, and 3rd order. 

tr, transverse vessel ; tr', tr", smaller transverse vessels. 

v.d, vas deferens. 

z, p'rebranchial zone. 

Plate XVI. 

Ascidia tritonis, n. sp. 

Fig. 1. — Ascidia tritonis, seen from the right side. Natural size. 
Fig. 2. — A small portion of the surface of the test. Slightly magnified. 

Fig. 3. — Another specimen, after the removal of the test, seen from the left side. Natural size. 
Fig. 4. — Part of the branchial sac, from the inside. Objective, Swift, 1 inch. 
Fig. 5. — Small portion of dorsal lamina, showing free edge. Objective, Swift, 1 iuch. 
Fig. 6. — Dorsal part of anterior end of branchial sac, showing tentacles, dorsal tubercle, peri- 
pharyngeal bands, &c. Objective, Swift, 1 inch. 

Plate XVII. 

Figs. 1 and 2, Ciona intestinalis, Linn. Figs. 3 and 4, Ascidia virginea, 0. F. Mliller. 
Figs. 5 and 6, Polycarpa pomaria, Sav. 

Fig. 1. — A small portion of the branchial sac of Ciona intestinalis, Linn., seen from the inside ; 

papilla? not represented. Objective, Swift, 1 inch. 
Fig. 2. — Another small portion of the branchial sac of Ciona intestinalis, from the inside. 

Objective, Swift, 1 inch. 
Fig. 3. — Ascidia virginea, 0. F. Miiller, var. pedunculata, from the left side. Natural size. 



Fig. 


1. 


Fig. 


2. 


rig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 



116 DR W. A. HERDMAN ON 

Fig. 4. — Dorsal part of anterior end of branchial sac of Ascidia virginea var. ■pcdnncidata, 
showing tentacles, dorsal tubercle, &c. Objective Swift, 1 inch. 

Fig. 5. — Polycarpa pomaria, Savigny, seen from the left side. Natural size. 

Fig. 6. — Part of the branchial sac of Polycarpa pomaria, seen from the inside, and showing 
two folds and two interspaces. Objective, Swift, 1 inch. 



Plate XVIIT. 

Doliolum denticulatum, Quoy and Gaimard. 

-Doliolum denticulatum from the right side. Natural size. 

-A specimen preserved in chromic acid and absolute alcohol, from the left side. 

Natural size. 
-The same specimen seen from the ventral surface. 

-A young individual (2 mm. in length) seen from the right side. Objective, Hart. 4. 
-Part of a muscle band from the mantle of a specimen preserved in picric acid. 

Objective, Hart. 5. 
-Another muscle band from the same specimen. Objective, Hart. 5. 
-Anterior half of endostyle, seen from the interior of the branchial sac, from specimen 
stained in picro-carmine. Objective, Hart. 4. 
Fig. 8. — Nerve ganglion, dorsal part of peripharyngeal band, &c, seen from interior of branchial 

sac. Objective, Hart. 4. 
Fig. 9. — Broad barrel-like form of Doliolum denticulatum, from left side. Natural size. 
Fig. 10. — Two specimens of the narrow elongated form. Natural size. 
Fig. 11. — Right side of branchial sac, &c, from interior. Reduced from Objective, Hart. 4. 
Fig. 12. — Nerve ganglion, neural duct, peripharyngeal band, &c. Objective, Hart. 5. 
Fig. 13. — Small part of peripharyngeal band, from specimen stained in osmic acid. Objective, 
Hart. 7. 

Plate XIX. 
Doliolum denticulatum, Quoy and Gaimard. 

Fig. 1. — Nerve ganglion and dorsal part of peripharyngeal band, from a specimen preserved 
in chromic acid and absolute alcohol, and stained in picro-carmine. Objective, 
Hart. 4. 

Fig. 2. — The ends of some of the stigmata, from a specimen preserved in picric acid. Objective, 
Swift, \ inch. 

Fig. 3. — Some of the ciliated cells bounding the stigmata, stained in picrocarmine. Objective, 
Hart. 7. 

Fig. 4. — Some of the ciliated cells bounding the stigmata, stained with osmic acid. Objec- 
tive, Zeiss, ^2, oil immersion. 

Fig. 5. — Some of the cells from the surface of the peripharyngeal band of a specimen pre- 
served in chromic acid, and stained in picro-carmine. Objective, Zeiss, ■f s , oil 
immersion. 

Fig. 6. — Part of the prebranchial zone in a specimen preserved in osmic acid and absolute 
alcohol. Objective, Hart. 7. 



THE " TRITON " TUNICATA. 117 

Fig. 7. — Part of the prebranchial zone enclosed by the coiled dorsal ends of the peripharyngeal 
band, from a specimen preserved in chromic acid and absolute alcohol, and stained 
in picro-carmine. Objective, Zeiss, fy, oil immersion. 

Fig. 8. — The anterior half of the nerve ganglion, showing the origin of the neural duct, from 
specimen stained in osmic acid. Objective, Zeiss, ^, oil immersion. 

Fig. 9. — Anterior end of the duct from the neural gland, showing its ciliated expansion and 
terminal aperture, from specimen preserved in osmic acid and absolute alcohol. 
Objective, Zeiss, y 1 ^, oil immersion. 

Fig. 10. — Posterior end of endostyle, oesophageal aperture, and the neighbouring part of the 
branchial sac, seen from the interior, from a specimen preserved in chromic acid 
and absolute alcohol, and stained in picro-carmine. Objective, Hart. 4. 

Fig. 11. — Part of the heart, from specimen shown in fig. 10. Objective, Hart. 7. 

Fig. 12. — Part of the ganglion, showing the origin of one of the nerves, from a specimen pre- 
served in picric acid and absolute alcohol, and stained in picro-carmine. Objective, 
Zeiss, y^, oil immersion. 

Fig. 13. — A group of nerve cells from the ganglion shown in figure 12. Enlarged from Zeiss, 
Objective yV^, oil immersion, ocular 4. 



Plate XX. 

Doliolum denticulatum, Quoy and Gaimard. 

Fig. 1. — Oesophagus, stomach, intestine, digestive glands, reproductive organs, &c, of an 
individual preserved in alcohol, and stained in picro-carmine. Reduced from 
Objective, Swift, 1 inch. 

Fig. 2. — Part of the duct (d) crossing from intestine to stomach in last figure. Objective, 
Zeiss, yV^, oil immersion. 

Fig. 3. — Part of the digestive gland forming a network of tubules over the intestine, from 
same specimen as fig. 1. Objective, Swift, £ inch. 

Fig. 4. — Part of the wall of the intestine, surface view. Objective, Hart. 5. 

Fig. 5. — Part of the organ (gl) seen ramifying over the stomach and first portion of the 
intestine in fig. 1, from specimen stained in picro-carmine. Objective, Zeiss, y^, 
oil immersion. 

Fig. 6. — The reproductive system dissected out. Reduced from Objective, Swift, 1 inch. 

Fig. 7. — The same in another specimen, showing a curious anterior termination. Reduced from 
Objective, Swift, 1 inch. 

Fig. 8. — Anterior extremity of the testis of another individual, stained in picro-carmine. Objec- 
tive, Swift, 1 inch. 

Fig. 9. — Anterior extremity of the testis in another specimen, preserved in solution of 
osmic acid. Objective, Hart. 5. 

Fig. 10. — Anterior extremity of the testis in another specimen, stained in picro-carmine. Objec- 
tive, Swift, 1 inch. 

Fig. 11. — Anterior extremity of the testis in another specimen. Objective, Hart. 5. 

Fig. 12. — Small part of the edge of the testis near the posterior end. Objective, Hart. 7. 

Fig. 13. — Opening of vas deferens close to ovary. Objective, Hart. 4. 

Fig. 14. — Aperture of vas deferens. Objective, Hart. 7. 

VOL. XXXII. PART I. U 



Trans. Roy Soc. Edvn 1 



Vol XXXII, Plate XVI. 



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FIG 5 5 & 6 POLYCARPA POMAR1A, Sav 



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DOLIOLUM DENT ICULATU M, q. &G . 



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( 119 ) 



VIII. — Report on the Pennatulida dredged by H.M.S. " Triton." By A. Milnes 
Marshall, M.D., D.Sc, M.A., Fellow of St John's College, Cambridge, 
Beyer Professor of Zoology in Owens College. (Plates XXI. to XXV.) 

(Read 16th July 1883.) 

Introduction. 

The Pennatulida obtained by H.M.S. "Triton," and placed in my hands for 
description, are of six genera only, each genus being represented by a single 
species. The interest of the collection is, however, far from commensurate 
with its size, for of the six species two are altogether new to science, a third 
has hitherto been met with only off the Norwegian coast, while concerning the 
remainder, which are well known species, the "Triton" specimens have furnished 
important additions to our knowledge, either of their anatomy or distribution. 

In arranging the species I have followed the system of classification pro- 
posed by Kolliker in his " Report on the Pennatulida dredged by H.M.S. 
'Challenger.'""" This scheme, though representing the latest results of our 
greatest authority on the group, cannot be considered altogether satisfactory, 
inasmuch as but very little attempt is made to express the mutual relations of 
the several groups, and highly specialised forms are mixed up with more primitive 
ones in a very confusing manner. I have, however, thought it better to adopt 
it here rather than attempt to frame a new scheme on inadequate material. 

The following outline of Kolliker's classification shows the position 
occupied by the genera with which we are concerned : — 

Order PENNATULIDA. 

Section I. Pennatule^e : polyps fused together to form leaves. 
Sub-section 1. Penni/ormes: leaves well developed. 
Family 1. Pteroeidiclae. 

Family 2. Pennatulidse. 

Genus Pennatula. 
Sub-section 2. Virgulariece : leaves small. 
Family 1. Virgularidse. 

Genus Virgularia. 
Family 2. Stylatulidse. 

Genus Dubenia. 

* Zool Chall. Exp., part ii. pp. 33-35, 1880. 
VOL. XXXII. PART I. X 



120 DR A. MILNES MARSHALL ON THE 

Section II. Spicatve : no leaves ; polyps sessile. 

Sub-section 1. Funiculinece : polyps arranged in distinct rows. 

Family 1. Funiculinidse. 

Genus Funiculina. 

Family 2. Stachyptilidae. 

Family 3. Anthoptilidse. 

Sub-section 2. Junciformes : polyps in single series or in indis- 
tinct rows. 

Family 1. Kophobelemnonidae. 

Genus Kophobelemnon. 

Family 2. Umbellulidse. 

Genus Umbellula. 

Family 3. Protocaulidse. 

Family 4. Protoptilidse. 

Section III. Renille^e : rachis expanded, in form of a leaf. 

Section IV. Veretille^e : polyps arranged on rachis in radiate manner. 

The following table shows the localities at which the specimens were 
obtained, the number taken at each, and the instrument employed in each case. 
The specimens taken at Stations 6 and 7 do not belong to the " Triton " collec- 
tion, but were dredged by the "Knight Errant" in 1880 : — 



Station. 


Locality. 


Depth in 
Fatlioms. 


Date. 


Name. 


Number. 


How 

Caught. 


6 


59° 37' N., 7° 19' W. 


530 


Aug. 11, 1880 


Kophobelemnon 


1 




7 


do. do. 


530 


Aug. 12, 1880 


Pennatula 


1 




8 


60° 18' N., 6° 15' W. 


640 


Aug. 22, 1882 


Kophobelemnon 


2 




10 


59° 40' N., 7° 21' W. 


516 


Aug. 24, 1882 


u 


3 

2 


Trawl 
Dredge 


11 


59°29'30"N.,7°13'W. 


555 


Aug. 28, 1882 


Pennatula 

Virgularia 

>) 

Diibenia 

Kophobelemnon 

» 
Umbellula 


18 
1 

2 

1 fragment 

1 

13 

11 & 6 heads 

1 


Trawl 

Dredge 

Trawl 

Dred 

Trawl 

Trawl 

Dredge 

Trawl 




Loch Linnhe, 
Off Castle Walker, 


1 35-37 


? 


Funiculina 


10 fragments 






Off Butt of Lewis, 


40 


Aug. 25, 1882 


Pennatula 


4 


Trawl 



PEKNATULIDA DREDGED BY H.M.S. "TRITON." 121 

Concerning the mode of capture, it will be seen from the above table that 
the trawl was distinctly more successful than the dredge ; and the difference 
between the two is greater than appears from a mere comparison of the number 
of specimens taken, for the proportion of imperfect and mutilated specimens 
brought up by the dredge far exceeds that yielded by the trawl, the mutilation 
being in many cases clearly caused by the dredge itself. 

For such forms as Pennatulida the dredge is indeed a very unsuitable 
instrument of capture ; a point that deserves a greater amount of practical 
attention than it appears yet to have received.* It is certainly worthy of note 
that the three most interesting forms collected by the " Triton " were all 
brought up by the trawl. 

Concerning the nomenclature adopted, I have retained the terms polyp and 
zooid for the two kinds of individuals, sexual and asexual, of which a Pennatulid 
colony normally consists, since these names are in general use. Strictly 
speaking, the names are objectionable, for the term zooid is commonly and con- 
veniently employed in zoology to indicate any member of a colony that is 
produced asexually, and in this sense both kinds of individuals of the Penna- 
tulid colony are zooids. 

For the tubular cavity into which the mouth leads, and which is commonly 
spoken of as the stomach, I have adopted the term stomodosum. This cavity is 
in no sense of the word entitled to the name of stomach, inasmuch as diges 
tion is effected, not in it, but in the body cavity into which it opens below. 
Kolliker has proposed to call it oesophagus,! but the term stomodceum seems 
preferable, as indicating at once its origin by involution of the outer layer of the 
body or ectoderm. 

Description of the Specimens. 

Order PENNATULIDA. 

Section I. Pennatule^e. 

Sub-section 1. Penniformes. 

Family 2. Pennatulidae. 

Pennatula, L. 
Pennatula phosphorea, L. (PI. XXI. figs. 4-7, and PI. XXII. figs. 8-16.) 
This species was obtained by the " Triton " at two localities, off the Butt of 
Lewis in 40 fathoms water, and at Station 11 at a depth of 555 fathoms. The 
collection also includes a single specimen obtained by the "Knight Errant" in 
1880. 

* Cf. Nature. A new dredging implement, voL xxvii. p. 11. 

f Kolliker, Anatorniscli-systematische Beschrelbung der Alcyonarien, p. 416, 1872. 



122 DR A. MILNES MARSHALL ON THE 

Of this very variable species Kolliker distinguishes three well-marked 
varieties, characterised as follows : # — 

1. Var. angustifolia : Leaves long and narrow; polyp heads few and wide 
apart. 

2. Var. lancifolia : Leaves lancet-shaped ; polyp heads numerous, and close 
together. Of this form, which should probably be considered the typical 
P. phosphorea rather than a distinct variety, Kolliker further distinguishes 
four sub-varieties. 

3. Var. aculeata : Leaves slender, and placed close together ; on the ventral 
surface of the rachis are four to six rows of long spines, connected with the 
zooids. 

Of the " Triton " specimens those obtained off the Butt of Lewis belong to 
the second variety lancifolia; while the more numerous specimens from the 
deeper water of Station 11 are typical examples of the variety aculeata. The 
two forms are so distinct that it will be well to describe them separately. 

P. pliosyliorea var. lancifolia, Koll. 

All four specimens are small, and of somewhat stunted appearance, the 
leaves being twisted in an irregular manner, so that sometimes the dorsal and 
sometimes the ventral border of the leaf is turned upwards. The four speci- 
mens, though of nearly the same absolute size and all obtained at one haul, 
differ a good deal among themselves as to the shape of the leaves and the 
breadth of their attachment to the rachis, and also as to the extent of separa- 
tion between the component polyps of a leaf. 

The zooids, which are uniform in size, cover the whole ventral surface of 
the rachis, except the mid-ventral groove, and extending upwards between 
the leaves, become continuous with small groups of three or four zooids each 
situated on the dorso-lateral angles of the rachis between the leaves. 

In all four specimens the stalk, with the exception of the terminal dilatation, 
which is yellowish, is of a dark red colour, due, as in the rachis and leaves, 
to the calcareous spicules imbedded in it. In one specimen the colour is a deep 
purple of exceptional intensity. 

The measurements of the four specimens in millimetres are as follows : — 

Length of colony, 

„ rachis, 

„ stalk, 

„ leaves, 
Greatest width of leaves, 
No. of leaves on each side, 
» polyps per leaf, 

* Kolliker, Anatomiich-systematisclie Beschreihung der Alcyonarien, pp. 130-134. 



A. 


B. 


C. 


D. 


60 mm. 


56 mm. 


58 mm. 


58 n 


31-5 


27 


31 


30 


28-5 


29 


27 


28 


13 


13 


12 


115 


2 


2-5 


3 


3 


20 


21 


22 


20 


10 


9 


9 


10 



PENNATTTLIDA DREDGED BY H.M.S. "TRITON." 123 

From these figures it will be seen that specimens A and B approach very 
closely Kolliker's variety angustifolia. 

P. phosphorea var. aculeata, KolL (PL XXI. figs. 4-7, and PL XXII. figs. 8-16.) 

This very well-marked variety, which does not appear to have been hitherto 
recorded from British seas, is characterised by the long and slender shape of 
the leaves (PL XXI. figs. 4 and 5), the small number of their component 
polyps, their distance apart, and the extent to which they are separate from one 
another ; and above <all, by the fact that a number of the zooids of the ventral 
surface (figs. 4 and 5,f) are very exceptionally developed — assuming the form 
of conical spines, which project from the rachis for a distance in some speci- 
mens of 3" 5 mm., or even more. 

This variety was first described in 1858 by Koren and Danielssen,* who 
found it at a single locality near Christiansund, where it occurred rather 
abundantly on clay bottom at the depth of 80 to 100 fathoms. Since then it 
has been taken by Sars at Christiansund at a depth of 30 to 70 fathoms, and 
in the Throndhjemsfjord in 100 fathoms water; by Carpenter and Wyville 
Thomson, during the "Porcupine " expedition in the Atlantic Ocean, 48° 26' N., 
9° 44' W., at a depth of 358 fathoms ; and by Whiteaves in the Gulf of St 
Lawrence, at a depth of 160 to 200 fathoms. 

Of the " Triton " specimens of P. phosphorea, all those, 19 in number, 
obtained at Station 11, depth 555 fathoms, belong to this variety, as also does the 
single specimen from the " Knight Errant" collection dredged at Station 7, in 530 
fathoms water. As the variety is a very interesting one, and has not yet been 
satisfactorily described, I have taken the opportunity afforded by the large number 
of specimens available to investigate in some detail the more important structural 
details, directing my attention more particularly to the large ventral zooids. 

The following table gives the measurements of the single specimen from the 
" Knight Errant " and of two of the " Triton " specimens. All the latter are of 
small size, the specimen B being one of the largest. 





A. 


B. 


C. 




" Knight Errant " 
Collection. 


" Triton ' 


Collection. 


Length of colony, 


70 mm. 


62 mm. 


48 mm 


„ racbis, 


31 


28-5 


24 


,, stalk, 


39 


33-5 


24 


„ leaves (longest), 


12 


13 


10 


Greatest width of leaves, 


3 


1-5 


1-5 


Number of pairs of leaves, 


19 


14 


10 


Number of polyps per leaf, 


9 


6 


7 


Length of largest zooids, 


3 


3-5 


3 



* Koren and Danielssen, Forhandlinger i. Videnskabsselskabet i. Christiania, p. 25, 1858; also 
Fauna Littorulis Norvegiw, part iii. pp. 86-88, and pi. ii. figs. 8 and 9, Bergen, 1877. 



124 DR A. MILNES MARSHALL ON THE 

Koren and Danielssen, Whiteaves and Verrill, maintain the specific 
distinctness of this form from P. phosplwrea. The measurements of the 
different specimens I have been able to examine show so great variability in 
the essential characters of the form, such as the length of the large zooids, 
width of leaves, &c, that I can have no hesitation in agreeing with Kolliker* 
in regarding it as merely a variety, though a very well-marked one. I cannot, 
however, accept RicmARDi'st conclusion that it is not even a variety, " ma uno 
stato puramente accidentale di certi exemplari." 

The general appearance of the form is shown in PI. XXI. fig. 4, representing 
an entire specimen seen from the right side and twice the natural size. Fig. 5 is 
a transverse section through the rachis about the middle of its length, with one 
of the attached leaves and the base of the corresponding leaf of the opposite 
side. For the sake of comparison, I have given in fig. 6 a similar view of a 
normal specimen of P. phosplwrea obtained from Oban. 

If these two figures be compared together, it will be seen that the points in 
which the variety aculeata (fig. 5) differs from the typical P. phosplwrea (fig. 6) 
are the following : — The leaf is longer and much narrower ; the polyps are fewer 
in number, are placed further apart, and are independent of one another for a 
greater portion of their length. The walls of the rachis are much thicker, a 
condition associated with the presence of larger and more numerous spicules ; 
the axial calcareous stem is thicker, and the main longitudinal canals of the 
rachis much smaller than in the typical form. Concerning the zooids, it will be 
seen that a very large one (fig. 6,/) arises from the rachis immediately below 
each leaf, with the ventral border of which it is fused for about a third of its 
length. Nearer the mid-ventral line of the rachis there is on each side a second 
row of large zooids, usually slightly smaller than those of the outer row, but 
sometimes equalling them in size; and within these again other zooids occur 
intermediate in size between the large ones and the normal small ones. The 
largest zooids, those attached to the ventral borders of the leaves, have an 
average length of rather over 3 mm. in the "Triton" specimens; in exceptional 
cases they reach 4 mm. 

Between the large zooids are numerous small ones of the normal size and 
character, which extend up the sides of the rachis between the bases of the 
leaves. 

That the connection of the large ventral zooids with the leaves is of a purely 
secondary nature is clearly seen by tracing their gradual development in passing 
upwards from the lower end of the rachis. At their first appearance they 
are small, identical in all respects with the normal zooids, and quite inde- 

* Kolliker, Op. cit., pp. 134 and 366. 

f lticuiARDi, Monoyrafia delict famiylia del Pennatularii, p. 24. 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 125 

pendent of the leaves, with which they become connate only after they have 
attained a considerable size. 

The structure of the large zooids, which does not appear to have been 
examined with any care hitherto, is shown in the series of figures on Plate XXII. 
Of these fig. 8 represents a median longitudinal section through the whole 
length of one of the zooids, and through the part of the rachis from which it 
springs ; while figs. 10 to 16 are transverse sections through a zooid at different 
parts of its length, fig. 10 being near to the apex and fig. 16 passing through 
the base of attachment of the zooid. 

The general anatomy of the large zooid is well shown in fig. 8, from which 
it will be seen that while agreeing in essential structure with the smaller and 
more typical zooids, it yet presents some points of special interest. 

The zooid is conical in shape, arising by a broad base from the rachis and 
tapering upwards rather sharply, ending in a pointed apex. As shown in figs. 
4 and 8 the zooid does not project horizontally outwards, but obliquely upwards, 
so that we can distinguish between an inner or axial surface, directed 
toward the rachis, and an outer or abaxial surface facing outwards. 

On the inner or axial surface, and nearer the base than the apex of the zooid, 
is the mouth (fig. 8, n). This leads into the stomodaeum s, which is lined by 
columnar ciliated ectoderm cells, the cilia clothing the outer or abaxial wall 
being of very great length, and forming with the surface of the stomodaeum 
from which they arise the structure which Mr Hickson has recently proposed 
to speak of as the siphonoglyphe.* 

The stomodaeum opens below into the general body cavity h, which is lined 
by endoderm, and is in communication with the cavities of the adjacent zooids 
and with, the main lateral canals of the rachis, and so indirectly with the 
polyps. The stomodaeum is attached to the body wall by the usual eight septa, 
which are well shown in the transverse section (fig. 15). Below the stomodaeum 
the two septa of the inner or axial surface, bounding the axial interseptal cavity, 
remain of considerable width, and bear at their free edges the two mesenterial 
filaments (figs. 8 and 16, p), which are very long and much convoluted, and 
extend down to the bottom of the zooid cavity. 

The other six septa become reduced immediately below the stomodaeum to 
very narrow ridges (fig. 16, m), which disappear altogether a short way lower down. 

The body wall of the zooid consists of an outer layer of short columnar ecto- 
derm cells, below which is the firm gelatinous mesoderm. This latter is much 
thicker on the outer or abaxial surface than it is on the inner or axial, and is 
strengthened by a great number of large calcareous spicules (figs. 8-16, i). 
These spicules are straight rods, thickest in the middle, and with rounded ends ; 

* Hickson, on the "Ciliated Groove (Siphonoglyphe) in the Stomodeeum of the Alcyonarians," Proc. 
Roy. Soc, 1883. 



126 DR A. MILNES MARSHALL ON THE 

the largest attain a length of 1*6 mm., with a width of 13 mm. In transverse 
section (figs. 10-16, i) the spicules are triangular, with rounded angles, and a 
shallow groove running somewhat obliquely down the middle of each face. 
They are exceedingly numerous along the whole length of the abaxial surface 
of the zooid, and are arranged with their long axes parallel, or nearly so, to 
that of the zooid. 

The mesoderm is traversed by a system of irregularly branching nutrient 
canals continuous with those of the rachis. The muscular system of the body 
wall of the zooid seems to be completely absent. 

The relations of the inter-septal chambers in the part of the zooid above the 
stomodreum are rather curious. Fig. 14 represents a transverse section through 
the mouth opening ; it shows that at this point only five of the eight inter- 
septal chambers are present, viz., the abaxial, or as it is commonly called, ventral 
cavity, the two latero-ventral cavities bounding it on either side, and the two 
lateral cavities ; the axial or dorsal and the two latero-dorsal cavities not 
ex-tending above the mouth. In a section taken a little higher up, through 
the upper part of the mouth (fig. 13), the two lateral cavities have dis- 
appeared, and the mid-ventral and latero-ventral cavities are alone present. 
Tracing them further up towards the apex of the zooid, we find that all three 
persist for some distance, but that after a time the middle abaxial or ventral 
cavity, which has been from the start the smallest (cf. figs. 15 and 14), loses 
its lumen (fig. 12), and then disappears altogether, the two latero-ventral 
cavities alone persisting (fig. 11). 

Further up still (fig. 10), one of the two latero-ventral cavities disappears 
and one alone is left, which can be traced nearly, or in some cases quite, up to 
the apex of the zooid. 

The prolongations upwards of the interseptal chambers above the mouth 
correspond, not to the tentacular cavities of the fully formed polyps, but to 
the cavities of the calyx processes ; and the whole of the part of the large 
zooid above the mouth is to be regarded as formed by a special unilateral 
development of the calyx, corresponding at its base to five, and along the 
greater part of its length to three calyx processes fused together, but with 
their axial cavities remaining distinct. 

That the spine of the large zooid really consists of calyx processes and not 
of tentacles, is, I think, proved by the perfect continuity between the wall of 
the zooid itself and the spine ; by the unbroken series of exceptionally large 
spicules extending along the abaxial wall of the whole length of the zooid, 
including the spine ; and by the absolute identity between a transverse section 
across the upper part of the spine, and one through a calyx process of a normal 
polyp. This latter point is well shown in figs. 9 and 10, the former being a 
section of a calyx process, and the latter of the spine of one of the large zooids. 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 127 

The agreement will be seen to be absolute, even as regards the actual size 
and arrangement of the spicules, which in both cases are far larger and more 
abundant on the abaxial or outer surface than on the axial or inner one. It 
is also worthy of note, in connection with the point in question, that in the 
development of the polyps the calyx processes appear earlier than the 
tentacles (vide fig. 7). 

The large zooids of P. phosphorea var. aculeata agree, therefore, with the 
zooids of Pennatulida generally in the complete absence of tentacles, as well as 
in the absence of reproductive organs and the possession of but two mesenterial 
filaments. They are peculiar merely in their very great absolute size, and in 
the prolongation of the abaxial surface to form the spine. 

The structure of one of the normal small zooids is shown in fig. 8, e. It will 
be noticed that here also the mouth, which in the early stages of development is 
terminal (as shown in the rudimentary zooid between e and the large zooid), 
becomes thrown over to the axial surface by growth forwards of the abaxial 
side, which forms a prominence above the mouth clearly comparable to the 
spine of the larger zooids. The figure shows also that the smaller zooids, like 
the large ones, possess the clothing of exceptionally long cilia on the abaxial 
surface of the stomodseum (siphonoglyphe of Hickson). 

The small zooid in question (fig. 8, e) is an immature one, as there is as yet 
no communication between the stomodseum and the body cavity of the zooid; 
the septa and mesenterial filaments have also not yet appeared. 

Panceri # has described and figured an interesting abnormality occurring in 
a specimen of P. phosphorea, in which four of the latero-yentral zooids, three 
on the left side of the rachis and one on the right, have the form and structure 
of fully developed polyps, inserted independently into the rachis, and attaining 
a length of 10 mm. and a diameter of 1 to 2 mm. In describing this curious 
modification, Panceri discusses briefly the mutual relations of polyps and zooids, 
points out the fundamental and essential correspondence between the two, and 
infers that the zooids must be regarded as abortive polyps, and that such cases 
as the one he describes are to be viewed as examples of reversion from the 
abortive to the fully developed condition. 

In this view Panceri is undoubtedly right. In a colony of individuals 
formed by continuous gemmation, i.e., by a process of budding in which the 
several zooids remain organically connected together to form the colony, the 
several component individuals must be supposed to be primitively all alike and 
equivalent to one another. Differences in structure and function could clearly 
only have arisen after the habit of forming colonies had been established for 
some time. Hence those colonies will be the most primitive in which there is 

* Panceri, " Intorno ad una forma non per anco notata negli zooidi delle pennatule," Rendiconto 
delVAcademia delle scienze fisiche e matematiche, pp. 23-28, Napoli, Febbrajo, 1870. 

VOL. XXXII. PART I. Y 



128 DR A. MILNES MARSHALL ON THE 

iu the adult form the smallest amount of difference between the constituent 
individuals ; while those forms in which this differentiation reaches its greatest 
development will be the most highly modified forms. These principles are of 
great importance in framing a scheme of classification of a colonial group such 
as the Pennatulida, and have not received sufficient attention in the classifica- 
tion at present in use. 

In the ordinary P. phosphorea the amount of differentiation is comparatively 
slight, and is brought about in the simplest possible manner ; the asexual zooids 
being simply arrested at what is merely an early stage of development in the 
case of the polyps. This is well shown in PL XXI. fig. 7, representing a 
side view of the lower end of the rachis, and showing the early stages of 
development of the polyps and zooids. 

The figure shows that the young polyps d are at first quite independent of 
one another, and that in their earlier stages they are absolutely identical with 
the zooids e ; and that the differences arise from the zooids becoming arrested 
at this early stage, while the polyps advance further, increase in size, acquire 
calyx processes /, and tentacles t, fuse with one another at their bases, so that 
their further increase in length gives rise to the leaf of the adult, and acquire 
the full number of mesenterial filaments, and ultimately reproductive organs. 

The differentiation is thus of the simplest possible character, the zooids 
being simply arrested or abortive polyps, whose function is apparently to main- 
tain currents of water circulating throughout the colony, for which purpose they 
have retained the sole structure peculiar to them — the clothing of exceptionally 
strong cilia on the abaxial surface of the stomodseum. As the siphonogiyphe is 
present in the mature polyps of many Alcyonarians, such as Alcyonium (vide 
Hickson, he. cit.), it seems certain that in the Pennatulida it is a structure that 
has been lost by the polyps, but retained by the zooids. 

In the variety aculeata differentiation has advanced further; and it is a 
point of importance to note that the points in which the large zooids differ 
from the small ones cannot be considered as repetitions of any part of the 
process by which the polyp is developed from the zooid condition. In the 
young polyp all the calyx processes arise simultaneously (fig. 7), as do also all 
the tentacles, so that the asymmetrical development of the calyx in the large 
zooids must be regarded as peculiar to and acquired by them. The lateral 
position of the mouth in the large zooids has apparently been acquired inde- 
pendently of and previous to the formation of the calycular spine, inasmuch as 
it is an equally prominent feature in the normal small zooids (fig. 8, e). 

Judging from their structure, the large zooids would seem to be protective 
in function, but as to the special circumstances which determine their develop- 
ment in particular forms, we are in complete ignorance. Were our knowledge 
confined, so far as these forms are concerned, to the " Triton " specimens, we 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 129 

should be greatly tempted to suppose that as one set of specimens — the typical 
P. phosphorea — is obtained from a depth of only 40 fathoms, and the other, 
the variety aculeata, from 555 fathoms, that the structural differences between 
the two forms may be at any rate in part due to the different external condi- 
tions of pressure, &c. 

Although, however, the variety aculeata does appear to occur as a rule 
in deeper water than the more normal form, yet this rule is not universal, for, 
as we have seen above/" Sars obtained specimens of aculeata off the Norwegian 
coast at depths of 30 to 70 fathoms. The determining cause therefore that 
leads to the production of the variety aculeata must be some other than mere 
depth, though this would appear to have some influence. 

It may be noticed, finally, that the vertical range of P. phosphorea, which 
KoLLiKERt puts at 30 to 300 fathoms, has been nearly doubled by the " Triton " 
dredgings, which show that the species lives in abundance, though in a rather 
diminutive form, as low as 555 fathoms. 

Sub-section 2. Virgulariece. 

Family 1. Virgularidae. 

Virgularia, Lam. 
Virgularia tuberculata, n. sp. (PL XXI. figs. 1-3.) 

Specific Characters. — Polyps nearly sessile, united at bases in groups of 
three, the groups alternating on the two sides of the rachis. Calyx completely 
obliterated when the polyp is fully protruded ; calyx margin marked by eight 
small tubercular processes placed opposite the tentacles. Reproductive organs 
in the immature leaves at the lower part of the rachis. Stem cylindrical. Colour 
of colony, yellowish-white. No calcareous spicules in any part. 

Habitat. — Station 11. 

Of this species three specimens were obtained, all of which are imperfect. 
The largest specimen (PL XXI. fig. 1) measures 68 mm. in length, and consists 
of the stalk and lower part of the rachis ; its upper end is abruptly truncated, 
and the upper 10 mm. of the stem are denuded of the fleshy sarcosoma. 

The second specimen is similar to the first, but smaller in all its dimensions ; 
it has a total length of 364 mm., and consists of the stalk and lower end of 
rachis, the upper end of which is abruptly truncated. 

The third specimen is 46 mm. long, and consists of the middle portion of 

the rachis of an apparently rather larger specimen than either of the other two ; 

truncated at both ends. 

* Supra, p. 123. 

f Zool. Chall. Exp., part ii. p. 38, 1880. 



130 DR A. MILNES MARSHALL ON THE 

The stalk of the first specimen (PL XXI. fig. 18) is cylindrical, with an 
average diameter of 21 mm. It presents a slight terminal dilatation at its 
lower end, and is marked on both dorsal and ventral surfaces by shallow median 
longitudinal grooves. The stalk has a length of 15 mm., and is continuous 
above with the rachis, the transition from one to the other being marked by 
the first appearance of the leaves. 

The lower part of the rachis is flattened dorso-ventrally, and has a transverse 
diameter of 2*6 mm. It is marked by upward continuations of the median 
dorsal and ventral grooves of the stalk. 

As we pass from the region with immature leaves to the part of the rachis 
bearing fully developed polyps, the rachis gradually becomes reduced in width, 
and in the upper part, where the polyps have attained their full size, it becomes 
cylindrical, with a diameter in the first specimen of - 5 mm., forming in fact 
a very thin fleshy investment to the stem. 

Tlie stem is cylindrical at its upper end, with a diameter of 4 mm.; it 
remains of nearly uniform size throughout the whole length of the rachis, but 
tapers gradually as it passes down the stalk. It is of considerable brittleness, 
especially in its upper part. 

The polyps commence in the lower part of the rachis as small transverse 
ridges placed very close together, the first 6 mm. of the rachis having 20 of 
these ridges on each side. Passing upwards, the ridges become more pro- 
minent, wider, and situated further apart, each being divided at its free edge 
into three polyps. 

Of the three polyps of a ridge, the dorsal one is from the start the smallest 
of the three, and the ventral one the largest; and these proportions are retained 
throughout. 

As the polyps get larger, the groups move further and further apart, until the 
interval between successive groups on the same side of the rachis is about 
3 mm., which appears to be the limiting distance. 

The ridges on the lower part of the rachis are so placed that while the 
dorsal polyps of the ridges of the two sides are almost in contact with one 
another in the mid- dorsal line, the ventral polyps are separated from one 
another by nearly the whole width of the ventral surface of the rachis, an 
arrangement which persists also in the fully formed polyps (fig. 2). 

The groups of polyps are from the first placed, not opposite one another, but 
alternately, as shown in figs. 1 and 2, the right hand group being a little in 
advance of the left one. 

The polyps of each fully developed group are almost completely independent 

of one another, their bases alone being united together, so that it is hardly 

possible to speak of distinct leaves. The inclusion of the species in the genus 

Virguldria is fully justified, however, by the general mode of development of 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 131 

the polyps, especially the simultaneous appearance of the component polyps of 
a group ; by the position of the reproductive organs in the immature polyps, 
the proportions of the stem at different heights, and by the existence of such 
forms as Virgularia bromleyi * in which the separation of the polyps is not 
carried quite so far as in V. tuberculata. From V. bromleyi, the new species is 
distinguished at once by the absence of calcareous spicules, and the presence of 
the tubercles marking the calyx margin. 

Concerning the development of the polyps, it can be ascertained by examina- 
tion of the immature polyps at the lower end of the rachis, that the stomodasum 
arises as usual as an involution of the ectoderm, appearing before the tentacles, 
which latter all develop simultaneously. In the early stages of development one 
tentacle is very commonly rather larger than the other seven, but whether this 
is an accidental feature or not I have been unable to determine, nor have I 
detected any constancy of position of the larger tentacle. In each group 
the ventral polyp is always the furthest developed, and the dorsal one the 
least so. 

In the smaller of the two specimens in which the stalk is perfect, the 
change from the immature to the fully developed polyps is a very abrupt one ; 
not gradual as in the larger specimen figured (PL XXI. fig. 1). The stalk in this 
smaller specimen is 8 mm. long ; the first 4 mm. of the rachis bear immature 
leaves only, and above this point the fully formed polyps commence abruptly. 

The fully expanded polyp (fig. 2) measures about 2 5 mm. in length, of 
which the tentacles form rather more than half; its width is about 0*2 mm. 
Opposite the insertion of the polyp, and for some little distance above and 
below it, the sarcosoma of the rachis is markedly thickened (fig. 2), giving the 
rachis at these places a quadrangular shape. The boundary line between the 
body of the polyp and the tentacles is indicated in the fully expanded polyp by 
a row of eight small knob-like processes placed opposite the tentacles (fig. 2). 
These processes are hollow, and consist of all three layers of the body wall — 
ectoderm, mesoderm, and endoderm ; they appear to correspond to the calyx 
processes of other Pennatulida. 

When the polyp is retracted, as in the lower specimens of fig. 2, these pro- 
cesses mark the line of invagination, and become much more consjDicuous, 
appearing as knobs placed round the edge of the calyx. 

In the " Triton " specimens, retraction of the polyp is never carried further 
than is shown in fig. 2, the fully retracted polyp being about half the length of 
the fully expanded one. Eetraction is probably effected slowly, as the great 
majority of polyps have died in an almost completely expanded state. 

The tentacles are rather longer than the body of the polyp ; are pinnated as 
shown in fig. 2, and present no special features of importance. 

* Kolliker, Zool. Chall. Exp., part ii. p. 9, 1880. 



132 DR A. MILNES MARSHALL ON THE 

The anatomy of the polyp, so far as I have had the chance of investigating 
it, agrees with that of other Virgularia?. The reproductive organs, as in 
Virgularia? generally, are contained, not in the mature polyps, but in the im- 
mature ones at the lower end of the rachis. 

The large specimen (fig. 1) is a male, and a small part of the rachis removed 
from a point 22 mm. from the lower end of the stalk, showed the mature male 
organs or spermatospheres. These (fig. 3) have the typical structure of the 
male organs of Pennatulids. They are oval or spherical bodies, the largest of 
which have a diameter of 0*38 mm." Each is enclosed in a very thin capsule, the 
contents of which are a mass of very minute brightly refracting bodies — the 
heads of the spermatozoa ; these are more closely packed at the periphery than 
in the centre, where a number of fine radiating filaments can be seen, which are 
probably the spermatozoa tails. 

The smaller specimen, in which the lower end of the rachis is present, was 
also -examined for reproductive organs, but none were found. The third 
specimen, consisting of the middle part alone of the rachis, is of course devoid 
of reproductive organs. 

This specialisation of the reproductive organs to the immature polyps is 
undoubtedly a sign of considerable differentiation, and marks Virgularia as a 
less primitive genus than such a form as Pennatula. For while in the latter 
the component individuals of the colony are of two kinds only — zooids and 
polyps — in Virgularia they are of three kinds — zooids, nutrient individuals, and 
reproductive individuals. Whether all the immature polyps ultimately develop 
into mature ones is uncertain ; probably not, inasmuch as all recorded specimens 
of Virgularia have immature polyps at the lower end of the rachis. The 
abrupt transition from the immature to the mature polyps described above as 
occurring in the second example of V. tuberculata, may perhaps indicate the 
existence of a sharp line of demarcation between the sexual and the nutrient 
individuals. 

Whether zooids are present or not in V. tuberculata, I have been unable to 
determine with certainty without destroying the specimens. Certain very small 
knob-like projections on the rachis near the base of the polyps may perhaps 
prove to be zooids ; if so, they are in an exceedingly rudimentary condition. 

As noticed above, all three specimens of V. tuberculata are imperfect, and 
their imperfection is of some interest, inasmuch as it is very characteristic of 
dredged specimens of Virgularia generally. Of the type species, V. mirabilis, a 
perfect specimen has never yet been seen, all the specimens recorded being 
fractured either at one or both ends. The lower ends or stalks are occasionally 
found perfect, but the upper end never, the only known exception being a 
single specimen in the Glasgow Museum. 

The cause of this mutilation has been elsewhere discussed. It has been 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 133 

suggested # that the lower fracture, which usually occurs about the junction of 
stalk and rachis, i.e., about the point of emergence from the mud of the sea 
bottom, is caused by the dredge at the moment of capture ; while the upper 
fracture is almost certainly effected quite independently of the dredge, and is 
perhaps due to the tops being browsed on as food by other animals. The 
great brittleness of the calcareous stem probably accounts for the readiness 
with which the specimens become broken, and the fact that of the three 
specimens of V. tuberculata, the one brought up by the dredge is broken at 
both ends, while the two taken with the trawl have their lower ends entire, speaks 
strongly in favour of the correctness of the first part of the above explanation. 
The measurements of the three specimens are as follows : — 







A. 


B. 


C. 


Total length, , 
Rachis, . . 




Upper end imperfect. 
68 mm. 
53 


Upper end imperfect. 
36-4 mm. 
28-4 


Both ends lost. 
46 mm. 
46 


Stalk, 




15 


8 


... 


Diameter of rachis, 




. 0-5 to 2-6 


0-4 to 2-1 


0-52 


„ stalk, 




2-1 


11 


... 


„ stem, 




0-4 


0-38 


0-4 


No. of polyps per leaf, 
Length of polyp, 
„ tentacle, 




3 

8 
1 


3 


3 
11 

1-4 


Distance of polyps apart 
Diameter of spermatospb 


(grea 
eres, 


test), 3 

0-38 


... 


3-1 



Family 2. Stylatulidae. 

Diibenia, Kor. and Dan. 
Diibenia dbyssicola var. smaragdina (Kor. and Dan.). (PI. XXIII. figs. 17-21.) 

A single fragment of this species was obtained from Station 11 at a depth 
of 555 fathoms. The specimen, which is imperfect at both ends, and has a total 
length of 61 mm., is represented from the ventral surface three times the natural 
size in PI. XXIII. fig. 17 ; while figs. 18 and 19 represent on a larger scale 
portions of the rachis as seen from the lateral and dorsal surfaces respectively. 

Inasmuch as the sole description that has yet appeared of this very beautiful 
form is the extremely short and imperfect account given by Koren and 
Danielssen,! I have thought it well to investigate and describe the " Triton " 
specimen as fully as could be done without injury to it. 

The rachis (figs. 17, 18, and 19) is cylindrical, and only slightly exceeds in 
diameter the cylindrical stem by which it is traversed throughout its length. 
At the upper end of the specimen the. stem projects bare for a length of about 

* Vide Report on the Oban Pennatulida, by A. M. Marshall and W. P. Marshall, 1882, pp. 57-60. 
f Fauna littoral is Norvegim, part iii. p. 26, and pi. x. figs. 7 and 8, 1877. 



134 BR A. MILNES MARSHALL ON THE 

3 mm. above the uppermost polyps, ending in an abruptly truncated and 
evidently broken extremity. At the lower end the fracture appears to have 
occurred about the junction of stalk and rachis, but the fleshy sarcosoma has 
been stripped off the lowermost 8 mm., leaving this part of the stem bare, and 
rendering it impossible to localise exactly the seat of fracture. The stem is 
quite as brittle as that of Virgularia, so that there can be little doubt that the 
cause of fracture is the same in the two cases. 

The entire specimen is of a pale yellowish-white colour, but has become a 
good deal discoloured in parts, apparently from the action of the spirit in which 
it was preserved. 

The polyps (figs. 17, 18, and 19) are arranged in pairs along the sides of the 
rachis, each pair being embraced at its base by the fan-shaped plate of cal- 
careous spicules k, so characteristic of the family Stylatulidce. The pairs of 
polyps are not inserted opposite one another, nor do they strictly alternate'; but 
those- of the left side are situated a little further forward, nearer the upper end 
of the rachis, than the corresponding pairs of the right side. 

The intervals between successive pairs of polyps on the same side of the 
rachis (fig. 17) gradually increase in passing upwards. At the lower end of the 
specimen the successive pairs are almost in contact with one another, but in 
passing upwards they move further and further apart, the intervals attaining a 
maximum a short way below the upper end of the specimen, above which point 
they decrease slightly, the polyps themselves also becoming smaller. 

The characters and relations of the fan-shaped spicular plates are well shown 
in figs. 18 and 19. Each plate is triangular, with the apex directed downwards 
and inserted into the rachis, and with its free upper edge surrounding the base 
of the pair of polyps to which it belongs. The plate is formed by the fusion of 
a number of radiately arranged spicules, of which the more deeply placed ones 
are smaller and completely fused together, while some of the more superficial 
ones are much larger, and not so closely fused. One of these large spicules is 
represented in fig. 21 ; it is widest near its lower end, and gradually tapers 
upwards to a point, which (figs. 18 and 19) projects freely for a short distance 
above the upper edge of the plate. These large spicules may attain a length 
of 23 mm. and width of 015 mm. From the apex of the spicular plate a 
number of smaller rod-like spicules (fig. 18) are continued for a variable distance 
down the rachis. 

The two polyps of each pair have their bases, which are covered by the 
spicular plate, fused together so as to form a rudimentary leaf. Above the 
level of the top of the spicular plate they are, however, completely free from 
one another. Of the two polyps, the dorsal one is always slightly smaller than 
the ventral one in accordance with the general rule among Pennatulida. The 
dorsal polyps of corresponding pairs are separated from one another by but a 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 135 

slight interval (fig. 19), while the ventral polyps are separated by the whole 
width of the ventral surface of the rachis. 

The polyps are retractile, and the extremes of contraction and expansion 
are represented in the two polyps of the upper pair in fig. 18. As the figure 
shows" there is no calyx formed during retraction, and the tentacles appear to 
contract to a less extent than the bodies of the polyps. As in the case of 
Virgularia tuberculata, the fact that the majority of the polyps have died in an 
expanded or half-expanded condition may be taken as evidence that contraction 
is effected slowly. 

Each tentacle is supported on its outer or aboral surface by a strong rib of 
calcareous spicules shown on a larger scale in fig. 20. These spicules are placed 
for the most part obliquely, running upwards and outwards; they have an 
average length of 0*13 mm. and diameter of 0*02 mm. They do not extend 
into the pinnules. 

At intervals along the body walls of the polyps spicules are found similar to 
those of the rachis, but rather smaller and less abundant. 

Concerning the reproductive organs I have no observations. According to 
Koren and Danielssen, # these are normally situated in the body cavities of the 
fully developed polyps in the genus Dubenia ; but a large polyp from the middle 
of the colony, which I opened for the purpose, had no trace of reproductive 
organs. 

The zooids are few in number, and very small and inconspicuous. They 
occur (fig. 19, e) as small rounded swellings on the dorsal surface between the 
pairs of polyps, and also on the sides of the rachis just above the polyps. 

The genus Dubenia was established by Koren and Danielssen in 1874,t and 
was at first named Batea, but that name being already appropriated for a genus 
of Crustacea, it was changed in 1877 to Dubenia. It includes those members 
of the family Stylatulidce in which the polyps, though fused at their bases, do 
not form distinct leaves, the fusion not extending above the calcareous fan- 
shaped spicular plate. The validity of the genus has been questioned by 
Verrill and by Richiardt, but is accepted by Kolliker in his Eeport on the 
" Challenger " Pennatulida, and may be considered as established. 

The " Triton " specimen has all the characters of Dubenia abyssicola var. 
smaragclina, as defined by Koren and Danielssen. ;{: This variety differs from 
the typical D. abyssicola in its more slender form, in its pale colour, and in 
having the polyps in groups of two instead of three or more. Koren and 
Danielssen express a doubt as to whether it should not be considered a 
distinct species rather than a mere variety, a doubt which I must share without 

* Op tit, p. 24. 

f Magazin for Naturvidenskaberne, 1874. 

| Koren and Danielssen, Fauna Uttoralis Norvegice, part iii. p 96, 1877. 
VOL. XXXII. PART I. Z 



13<j DR A. MILNES MARSHALL ON THE 

attempting to remove, as I have had no opportunity of examining specimens of 
the typical D. abyssicola. 

The variety smaragdina has hitherto only been recorded from the Rams- 
fjord close to Alvcerstronimen, two miles from Bergen, where it was found "at 
a depth of 100 to 120 fathoms on a clayey sand bottom," in company with the 
typical D. abyssicola, but in smaller numbers. 

The measurements of the " Triton " specimen are as follows, those of two 
specimens described by Koeen and Danielssen being given for the sake of 
comparison : — 



" Triton " specimen, imperfect 
at both ends. 


Swedish 


specimens, 


entire 




Total length, .... 


61 mm. 


268 


mm. 


200 mm 


Rachis, 


61 


197 




148 


Stalk, 


absent 


71 




62 


N6. of pairs of polyps, 


34 


54 




44 


Diameter of rachis, 


0-36 








Diameter of stem (at top), 


0-32 










Length of fully expanded polyp, 


4-5 


... 








„ tentacle, . 


2-4 


. . . 








Length of retracted polyp (inch tentacle), 2 










Size of large spicules of calyx, 


2-3x015 










„ tentacle, 


013 x 0-02 










Size of spicules of body wall of polyp, 


0-56 











Section II. Spjcat^e. 

Sub-section 1. Funiculinece. 

Family 1. Funiculinida?. 
Funiculina, Lam. 

Faniculina quadrangularis, Pall. (PI. XXIII. fig. 22.) 

Ten fragments of this species were obtained by the " Triton " in Loch 
Linnhe, off Castle Walker, in 35 to 37 fathoms of water, and at a distance of 
3£ miles from the shore. 

All the specimens are small and imperfect. Two of them, of 9*4 and 
12*5 cm. length respectively, have the stalks perfect, and are broken short 
above at the lower part of the rachis. The remainder are all mere fragments 
broken at both ends, and varying in length from 5 to 34 cm.. 

None of the specimens have the upper ends perfect, a very unusual circum- 
stance with this species, which is usually obtained in perfect condition. The 
specimens have, however, evidently been roughly handled, and were probably 
damaged at the time of capture. 



PENNATULIDA DREDGED BY H.M.S, " TRITON." 137 

All the fragments belong to small and young specimens. Inasmuch as F. 
quadrangularis is found at other parts of Loch Linnhe in great profusion and 
of large size, specimens having been obtained up to 162 cm. in length, it 
would appear that the locality from which the " Triton " specimens were 
obtained is not one favourable to this species. 

The portion of rachis of one of the young specimens drawn in fig. 22 shows 
some points of interest. In the first place, it will be noticed that the calcareous 
spicules, which in F. quadrangularis are usually confined to the calyx, here 
extend down the whole length of the polyps along the lines of attachment of 
the septa. These spicules, which also occur in the rachis, though in smaller 
numbers, have an average length of 1 "7 mm. The unusual abundance of these 
spicules, and their presence in such young specimens, are points of interest. 

The middle polyp of the figure is shown in a condition of extreme contrac- 
tion ; the tentacles being completely withdrawn within the calyx, the processes 
of which meet one another so as to form an acutely pointed cone. This figure 
agrees very closely with one given by Kolliker,* the accuracy of which has been 
doubted, owing to the shape being so very unlike that of the expanded or half- 
expanded polyp, and the apparently exaggerated length of the calyx processes. 

Fig. 22 shows also the gradual increase in size of the polyps in passing 
from the dorsal (right-hand surface in the figure) to the lateral surface ; also 
the entirely independent insertion of polyps and zooids — a primitive feature ; 
and the total absence of distinction between the young polyps and the zooids ; 
also the quadrangular shape of the stem. 

Sub-section 2. Junciformes. 

Family 1. Kophobelemnonidae. 
Kophobelemnon, Asbjornsen. 

Kophobelemnon stelliferum var. durum (Koll.). (PL XXIV. figs. 23-28.) 

Thirty-three entire specimens of this species and seven heads (the upper 
polyp-bearing part of the rachis) were obtained, one of these being from the 
" Knight Errant " collection, the remainder from the " Triton " one. They 
were dredged at four different localities, Stations 6, 8, 10, and 11, and at 
depths varying from 516 to 640 fathoms. 

K. stelliferum was first found by 0. F. Muller in 1775, near Drobak, in the 
Christianiafjord, and described by him in the Zoologia Danica, under the name 
Pennatula stellifera. It has been dredged in various parts of the Christiania 
fjord by Loven and by Asbjornsen, t the latter of whom obtained it in con- 

* Kollikee, op. tit, pi. xvii. fig. 153. 

f Asbjornsen, " Beskrivelse over Kophobelemnon Miilleri," Fauna littoralis Norvegice, Andet 
Hefte, pp. 81-85, and Tab. 10, figs. 1-8, 1856. 



138 DR A. MILNES MARSHALL ON THE 

siderable numbers at a depth of about 40 fathoms, and of sizes varying from 
20 mm. long, with only a single polyp, to 125 mm. long, with 24 polyps. 

A single specimen was obtained by Panceri from the Bay of Naples,* and 
during the " Porcupine " expedition two specimens were obtained by Carpenter 
and Wyville Thomson t off the N.W. coast of Scotland, — one in 59° 41' N., 
and 70° 34' W., at a depth of 458 fathoms, the other in 59° 34' N., and 7° 18' 
W., and at 542 fathoms depth. 

External Characters. — The " Triton " specimens vary much in size, and in 
the number and arrangement of the polyps. The smallest specimen is 26 mm. 
long, and has only two polyps ; the largest specimen in the collection, the 
single specimen obtained by the " Knight Errant," is 88 mm. long, and bears 
18 polyps. 

The general appearance of one of the average specimens of the " Triton " 
collection is well shown in PL XXIV. fig. 23 ; the specimen being drawn from 
the dorsal surface, double the natural size. 

The rachis, which is somewhat club-shaped, is widest a short distance below 
its upper end, from which point it tapers upwards to a blunt point. It bears 
on its dorsal and lateral surfaces the polyps, which are few in number, and of 
large size. Between the polyps the surface of the rachis is studded on all 
sides with zooids, excepting a short tract immediately below each of the 
polyps, which is destitute of zooids. 

The stalk (fig. 23, b), which forms rather more than half the entire length of 
the colony, and which is distinguished from the rachis by bearing no zooids, 
is oval in section, as shown in fig. 27, and of tolerably uniform size along its 
whole length, except at its lower end, which presents a terminal thin- walled 
dilatation. 

The arrangement of the polyps differs a good deal in different specimens, and 
it is difficult to make out any definite system. In all cases the uppermost 
polyps, those nearest the top of the rachis, are the largest, and the lowest ones 
the smallest. The most usual arrangement is that shown in fig. 23. Here 
there are six fully developed polyps arranged in two sets, an upper and a lower 
one, each of three polyps. Of these three, one is inserted in the dorsal surface 
of the rachis very close to the mid-dorsal line, or actually in it, while the other 
two are inserted on the sides of the rachis a little way below the dorsal polyp, 
and not quite opposite one another, the right hand polyp being as a rule a little 
above the left hand one. The three polyps of each set are of about equal size, 
but those of the upper set are much larger than those of the lower set. Below 
the lower set can be seen in many specimens, as in the one figured, a third set of 

* Panceri, " Intorno a due Pennatularii l'uno non per anco trovato nel Mediterraneo, l'altro 
nuovo del nostra golfo," Rendiconto ddV Accidentia delle scienze fisiche e matematiche, Napoli, 
Giugno, 1871. 

t f Vide Kolliker, op. cit., p. 306. 



PENNATULTDA DREDGED BY H.M.S. " TRITON." 139 

very small and as yet rudimentary polyps, arranged in a manner exactly corre- 
sponding to the upper sets. 

It is clear that this arrangement might also be described by saying that the 
polyps are arranged in three longitudinal series, one dorsal and two lateral, the 
members of each series decreasing in size from above downwards, and this is 
indeed the method usually adopted. I am disposed, however, to prefer the 
former mode of description, because it seems to me from an examination of a 
number of specimens, that the three polyps of each set arise simultaneously, or 
very nearly so, the dorsal polyps being often a little ahead of the lateral ones, 
and the right lateral polyps appearing sometimes a little earlier than the 
left ones. 

There appears, indeed, to be a fair amount of constancy in the arrangement 
and order of appearance of the polyps. Of twelve specimens, four had 3 polyps 
only, which were clearly the three of the upper set ; five had 6 polyps arranged 
as in fig. 23 ; one had 4 polyps, i.e., the 3 of the upper set and the second dorsal 
one ; and the other two had 4 and 5 polyps respectively arranged in an irregular 
manner. In specimens with a larger number of polyps than six, it is very 
difficult to make out any definite plan of arrangement. 

Structure of Polyps. — This has been very fully described by Kolliker,* and 
will not be considered here in any detail. The main points are shown in the 
figures 24 to 28. The mesoderm is everywhere, both in stalk, rachis, and 
polyps, of considerable thickness, and has an immense number of calcareous 
spicules imbedded in it (figs. 27, 28). Each tentacle (figs. 24 and 25) has 
along its outer surface a prominent rib, made up of closely packed spicules, 
while smaller ones extend along the pinnules, as first noticed by Panceri. 

The spicules of the tentacular rib, which may attain a size of 0"66 by 01 1 
mm., are of the shape shown in fig. 26, and in transverse section in fig. 25. 

The polyps project from the rachis nearly at right angles, as shown in fig. 
23, and the polyp cavities on reaching the rachis do not stop, but bending 
down at right angles to their former course, are continued for some distance 
down the rachis, ending blindly below; the lower part of the stomodseum, and the 
whole of the organs below the stomodaeum being thus contained within the 
rachis. The greater part of the thickness of the rachis is, in fact, made up 
of these lower ends of the polyps, which in a transverse section of the rachis 
will be seen cut at various levels. 

Fig. 28 represents such a section. On the left side it cuts one of the 
lateral polyps longitudinally and horizontally (cf. fig. 13) ; on the right side it 
cuts the corresponding polyp of that side lower down, the section passing 
transversely through the lower part of the stomodseum. The dorsal polyp 
of the set is cut at a still lower level, the section passing through the two 
long mesenterial filaments and the ova. 

* Op. tit., pp. 297-304. 



140 DR A. MILNES MARSHALL ON THE 

The section also shows four zooids cut, like the polyps, in different planes 
and at different levels. 

Plane of Symmetry. — Each polyp of a Pennatulid colony can be divided 
longitudinally into two perfectly similar halves by one plane only, which is 
spoken of as the plane of symmetry. This plane passes between the two long 
mesenterial filaments, bisecting the septal chamber bounded by the two septa 
which bear these filaments ; it also bisects the septal chamber immedi- 
ately opposite to this one, and passes along the long axis of the stomodasum, 
which in transverse section (fig. 28, s) is oval, not circular in shape. In 
Kophobelemnon this plane of symmetry of each polyp has a very definite 
relation to the rachis. The plane is a vertical one, and is perpendicular to the 
surface of the rachis to which the polyp is attached, so that if prolonged it 
would pass through the centre of the calcareous axis or stem. These relations 
will become more obvious from an inspection of fig. 28. In the case of all three 
polyps shown in this figure, the planes of symmetry, being vertical when the 
specimen is placed upright in its natural position, will be at right angles to the 
plane of the paper. In the case of the dorsal polyp the plane of symmetry 
must pass through the centre of the polyp cavity, and must also (by definition) 
pass midway between the two long mesenterial filaments p ; it is obvious from 
this figure that this plane, if prolonged, will pass through the centre of the 
calcareous stem c. 

So also in the case of the right hand polyp of the figure. In order to 
divide the retractor muscles rm symmetrically, it is clear that the plane of 
symmetry must bisect the septal chamber next to the stem c, and also the 
chamber immediately opposite to this one ; such a plane will pass along the 
longer axis of the stomodaeum s, and will, if prolonged, pass through the 
centre of the stem c. 

So with all the other polyps, the plane of symmetry will always be a 
vertical one, will be at right angles to the surface of the rachis at the point of 
insertion of the polyp, and will, if prolonged, pass through the centre of the 
calcareous stem. 

It is further evident from fig. 28 that the two long mesenterial filaments are 
on the side of the polyp next to the stem, so that the surface of the polyp 
which, when the polyp becomes free from the rachis (cf. fig. 23), is continuous 
with its upper surface, may conveniently be called the axial surface; while the 
opposite surface, which is furthest from the stem, and which is continuous with 
the lower surface of the polyp when this becomes free from the rachis, may be 
called the abaxial surface. 

I have already used the terms axial and abaxial when describing the 
surfaces of the Pennatula zooids," and have done so in exactly the same sense 

* Supra, p. 125. 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 141 

as that here proposed, the axial surface being that which bears the long 
mesenterial filaments. As these words express a real and an important rela- 
tion, they would appear preferable to the very misleading terms dorsal and 
ventral, which are commonly employed to denote the surfaces in question. 

The plane of symmetry of the zooids obeys exactly the same laws as that 
of the polyps, the mesenterial filaments being placed on the axial wall. 

Concerning the arrangement of the zooids on the rachis, it will be seen from 
fig. 28 that the reason of the existence of a short tract devoid of zooids imme- 
diately below each polyp is that this tract is really part of the dbaxial wall of 
the polyp; and as the zooids are developed on the rachis itself and not on the 
polyps, there can clearly be no zooids on these tracts. 

Retraction of Polyps. — In spite of the great rigidity of the wall both of the 
polyp itself and its tentacles, due to the enormous number of spicules contained 
in it, the polyps can, as shown on the right-hand side of fig. 23, be withdrawn 
almost completely into the rachis, the tentacles entirely disappearing from 
sight in the fully retracted state. During the process of retraction the body 
wall of the polyp is thrown into transverse folds, and one specially deep fold 
at the junction of body and tentacles {vide the left-hand polyp of fig. 28) corre- 
sponds to the calyx of other Pennatulida. 

Structure of Stalk. — This is well shown in fig. 27, representing a transverse 
section taken about the middle of its length. The mesoderm is of great 
thickness, and is divided into inner and outer zones by the well-developed 
layer of longitudinal muscles Im, which forms a deeply corrugated sheath 
extending round the whole stalk. Of the two zones the outer one is very 
richly studded with calcareous spicules i, crossing one another in all possible 
directions ; while the inner zone is devoid of spicules, and is traversed by a 
dense network of nutrient canals. The stem c is quadrangular, with rounded 
angles and grooved lateral surfaces. In the rachis, as we have seen (rig. 28), the 
stem is cylindrical; but this change in shape is by no means exceptional, 
occurring in Pennatula and several other genera, as well as in Kophobelemnon. 

The stem is invested by a mesodermal sheath, which is prolonged outwards 
to the body wall as four vertical septa, which separate from one another the 
four main longitudinal canals of the stalk, of which the dorsal dc, and ventral 
vc, are considerably larger than the lateral ones Ic. If these canals, which are 
lined by endoderm, be traced upwards towards the rachis, the two lateral ones 
are soon found to disappear ; the dorsal one extends a short distance up the 
rachis, and then in its turn disappears, while the ventral one (fig. 28, vc) 
persists of considerable size throughout the whole length of the rachis. 

Of Kophobelemnon stelliferum Kolliker* distinguished at first two varieties, 
which he named mollis and dura respectively, the difference consisting chiefly 

* Kollikbr, op. cit., p. 305. 



142 DR A. MILNES MARSHALL ON THE 

in the greater number and size of the spicules of the latter, which reach in the 
tentacles a length of from 0*64 to 089 mm. and width of 0'09 to 0*12 mm. 
The muscular layers are also far less strongly developed in the var. dura than 
in var. mollis. 

At a later period* he described a specimen from the Atlantic at a depth of 
690 fathoms, which was in all its characters intermediate between the two 
other forms, and seemed to prove them to be merely varieties, and not, as once 
supposed, specifically distinct. 

The "Triton" specimens belong clearly to the variety dura, though they 
differ a good deal among themselves as to the size of the spicules. The single 
specimen from the " Knight Errant " collection has much smaller spicules than 
any of the others, and is to be referred to the variety intermedia. 

The following table gives the measurements of the " Knight Errant " speci- 
men and of one of the typical " Triton " specimens : — 









A. 






B. 








Var. intermedia 






Var. dura 








from " Knight Errant." 






from "Triton." 


Total length, 






82 mm. 






45 mm. 


Length of rachis, 






435 






21 


„ stalk, 






38-5 (broken 


at lower 


end) 


24 


No. of polyps, . 






18 






6 


Size of spicules (largest), 


0-31 x 0-018 






0-66x011 



All the specimens of K. stelliferum were encrusted rather thickly with sand, 
which adhered somewhat firmly to the ectoderm, and doubtless acted in part 
as a protective envelope. The internal cavities, both stomodseum, body cavity, 
and tentacular cavities, also contained large quantities of sand, which rendered 
the preparation of sections a matter of some difficulty. Whether this indicates 
a habit of retraction into the sand in which they live planted by their stalks, or 
whether the sand is purposely swallowed for the sake of food matters that may 
be mixed with it, I have had no opportunity of determining. 

Family 2. Umbellulidae. 

Umhellula, Lam. 

Umhellula gracilis, n. sp. (PI. XXV. figs. 29-35.) 

Specific Characters. — Distinctly bilateral. Polyps, forming a cluster on the 
upper end of a club-shaped rachis ; greyish in colour with dark reddish-brown 
tentacles. Stalk long, very slender and exceedingly flexible ; ending below in 
a dilated vesicular portion. Zooids numerous on the rachis between the polyps, 

* Op. cit., p. 320. 



PENNATULIDA DREDGED BY- H. M.S. "TRITON." 143 

and extending a short distance below them; zooids of upper part of rachis 
much the largest, and each provided with a tentacle bearing a double row of 
pinnules ; zooids of lower part of rachis are smaller, — they may have tentacles, 
but these do not bear more than a single pinnule. Stem cylindrical along the 
greater part of its length, becoming quadrangular in the terminal dilated part. 
No calcareous spicules at any part of the colony. 

Habitat. — Station 11 ; depth 555 fathoms. 

External Characters. — A single specimen of this species was obtained 
with the trawl. This specimen, which is in perfect condition, is represented 
of the natural size, and from the dorsal surface in PL XXV. fig. 29. It has a 
total length of 290 mm., of which the upper 26 mm. are expanded to form the 
club-shaped rachis. This ends above in a blunt point (fig. 30), and is widest about 
the middle of its length, where it measures 6 mm. from side to side, and 5 mm. 
from the dorsal to the ventral surface. 

The rachis bears the polyps on the upper two-thirds of its length, and below 
the lowest polyp tapers somewhat rapidly, and passes without any sharp line of 
demarcation into the stalk. 

The stalk is cylindrical and very slender, with a diameter about the middle 
of its length of 0*8 mm. At its lower end it presents a distinct enlargement, 
35 mm. long and 3*5 mm. in diameter. For the greater part of its length the 
stalk is extremely flexible, so much so that it can readily be coiled in circles of 
5 mm. diameter without the slightest danger of breaking. 

The stem or calcareous axis is cylindrical along the greater part of the 
length of the stalk, with an average diameter of 0*5 mm. Shortly before 
reaching the terminal dilatation of the stalk the stem enlarges somewhat 
suddenly to 9 mm. in diameter, becoming at the same time quadrangular in 
shape, and very much more rigid than in the upper part. In the terminal 
dilatation it gradually tapers towards the lower end. 

The polyps, which are confined to the upper 18 mm. of the rachis (figs. 29 
and 30) are 13 in number, and gradually increase in size from above down- 
wards. They are inserted on all sides of the rachis, with the exception of a 
narrow strip 1*5 mm. wide along the mid-ventral surface (fig. 30), and even this 
is somewhat encroached upon by the lowest polyps. 

It is difficult to make out any definite plan of arrangement of the polyps. 
Commencing at the top, the first polyp, which is the smallest of the lot, is 
inserted in the left latero-dorsal surface just below the apex. The second 
polyp is placed on the right latero-dorsal surface, a little way below the first. 
Then comes a rather irregular whorl of six polyps, of which two are dorsal, 
two lateral, and two latero- ventral ; and finally a lower whorl of five polyps, 
the largest of all, of which one is mid-dorsal, two lateral, and two latero-ventral, 
the left one of the last pair almost reaching the mid-ventral line. 

VOL. XXXII. PAKT I. 2A 



144 DR A. MILNES MARSHALL ON THE 

The body of the polyp is greyish in colour, and from 10 to 15 mm. in length. 
It is widest at its base— 4 mm. in the larger polyps, and gradually narrows in 
its upper third to 25 mm. The upper part is marked by very distinct longi- 
tudinal grooves opposite the septal attachments, and is also slightly corrugated 
transversely. 

The tentacles are of a dark reddish-brown colour, and of about the same 
length as the polyp body. Each is fringed by a double row of pinnules, which 
exhibit an irregular alternation of larger and smaller ones (fig. 31); the larger 
pinnules being inserted rather nearer the inner or oral surface of the tentacle 
than the small ones. Lindahl* has directed special attention to this inequality 
of the pinnules in the case of U. Lindahli (Koll.)t, where it appears to be much 
more marked than in U. gracilis. 

The polyps and tentacles are non-retractile, or can at most be withdrawn to 
a very slight extent, and there is no trace of a calyx. 

Structure of Polyp. — One of the polyps was removed for the sake of 
studying its structure, and cut into a series of transverse sections. The 
anatomy presents no points of special importance. The body wall is of only 
moderate thickness, the body cavity and tentacular cavities being of large size. 
As in Kophobelemnon the polyp cavities are prolonged into the rachis, but a 
larger proportion of the polyp is free than in this genus ; the stomodseum and 
upper part of the mesenterial filaments being contained within the free part of 
the polyp, and the reproductive organs and lower part of the mesenterial fila- 
ments being alone situated within the rachis. 

The plane of symmetry in the case of the one polyp examined, and pre- 
sumably in the others as well, obeys the same laws that have been found above 
to apply to Kophobelemnon and Pennatula, i.e., it is vertical and at right angles 
to the surface of the rachis at the point of insertion of the polyp. The axial surface 
of the polyp, moreover, is that which bears the two long mesenterial filaments. 

The single specimen obtained is a female, and the arrangement of the 
reproductive organs is the same as in other Pennatulida, the ovaries being the 
free edges of the six septa which bear, higher up, the six short mesenterial 
filaments. Fig. 34 represents a section of one of these fertile septa and of the 
part of the body wall from which it springs. The figure shows the largely 
developed retractor muscle of the polyp rm, and at the edge of the septum ova 
in various stages of development, each with a large nucleus and nucleolus, and 
invested in a distinct epithelial capsule. The ripe ova have a diameter of 
01 mm. 

* Lindahl, "Om Pennatulid-sliigtet Umbellula," Kongl. Svenska Vetenshaps-Altademiens Handling u r, 
Bd. xiii. No. 3, Stockholm, 1874. 

t KoLLiKEit, Die Pennatulide Umbellula, Wurzburg, 1875. Kolliker proposes to group together 
I.indaul's U. miniacea and U. pallida under the name U. lindahli. 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 145 

The specimen being in excellent histological condition, I have been enabled 
to make some observations on the development of the ova. Fig. 35 represents 
a transverse section through one of the ovigerous septa close to its free inner 
edge. The septum is seen to consist of a central mesodermal lamella x, clothed 
on each side by a thick layer of endodermal cells y. Of these cells the super- 
ficial ones form a layer of short columnar or cubical cells, while the remainder 
of the endoderm consists of larger cells of irregular polygonal shape, closely 
packed together, with large granular but rather ill-defined nuclei and granular 
protoplasm. 

Among these cells certain ones are conspicuous by their larger size and 
granular appearance, o'. These, which are the germinal cells or primitive ova, 
appear to arise in the deeper parts of the endoderm layer close to the meso- 
derm lamella, and as they increase in size gradually move outwards towards 
the surface. 

Together with this increase of size the ova become spherical in shape, the 
protoplasm becomes very granular and opaque, and the nucleus, which at first 
was an ill-defined granular body, becomes vesicular, and acquires a distinct 
nucleolus and a very well-marked nuclear reticulum. In some of the larger 
ova o, a reticular appearance is also evident in the protoplasm. 

The ovum, by its continued growth, reaches the surface of the septum, and 
pushing before it the surface layer of columnar epithelium, which forms the 
follicular investment, projects freely from the surface to which it remains 
attached by a short stalk (fig. 34). 

In Sagartia, according to the Hertwigs,* the ova arise in the deeper layer 
of the endoderm, but sink into and become invested by mesoderm before com- 
mencing their outward passage towards the surface of the ovary. I have seen 
no trace of such a mesodermal investment in Umbellula, neither have I seen the 
peculiar polar fibrillar apparatus described in Sagartia. 

Structure of Zooids. — The zooids of U. gracilis are unique among Penna- 
tulida, so far as at present known, in possessing pinnated tentacles. 

As shown in fig. 30, the zooids cover all parts of the rachis not occupied by 
the polyps. The largest zooids are those at the upper end of the rachis, and 
it is in this situation alone that the zooids with pinnated tentacles occur. Below 
the polyps the zooids get gradually smaller and smaller. 

Fig. 32 represents on a larger scale a group of zooids from the ventral 
surface of the upper extremity of the rachis, drawn with the camera. The 
zooids are seen to be conical, in the best marked cases tubular, projections with 
a mouth at the free end overhung by a single tentacle, which bears a variable 
number of pinnules. The pinnules may occur on one side only or on both, 
and in some cases form a row of five or six on each side of the tentacle. 

* 0. und R. Hertwig, Die Aetinien, pp. 95 seq. 



146 DR A. MILNES MARSHALL ON THE 

In fig. 33 one of these zooids is represented in longitudinal vertical section, 
together with the part of the rachis from which it springs. 

The tentacle, which is hollow, overhangs the mouth on the abaxial side. 
a point of some interest, inasmuch as the calycular processes of the large 
ventral zooids of P. phosphorea var. aculeata were also found to be abaxial 
(cf. PL XXII. fig. 8). 

The mouth n leads into the stomodaeum s, the abaxial wall of which is 
clothed with very long cilia r. At its lower end the stomodseum opens into 
the body cavity h, which is lined by endoclerm, and is prolonged into the 
tentacle. The body cavity is, at any rate in some cases, in direct communication 
with that of adjacent zooids. 

As in zooids generally, there are only two mesenterial filaments present, of 
which one is shown in the figure. These are borne by the axial septa, and are 
extremely long and much convoluted. 

In some of the larger zooids I have noticed a slight notching of the margin 
of the mouth, which may possibly indicate the rudiments of additional ten- 
tacles. 

Below the polyp-bearing part of the rachis the zooids become much smaller. 
The tentacles at first increase slightly in length, but become much more slender, 
and lose their pinnules, with the exception of a single one, which is often 
retained, giving a bifid appearance to the tentacle. These tentaculiferous 
zooids are, as shown in fig. 30, almost confined to the lateral margin of the 
rachis, the zooids of the dorsal and ventral surface becoming very early reduced 
to the condition of small wart-like knobs. These become 'smaller in size and 
more irregular in arrangement as we pass downwards, and finally cease about 50 
mm. from the upper end of the rachis. 

In possessing single tentacles the zooids of U. gracilis resemble those of U. 
Huxleyi and U. Carpenteri* two of the species obtained by the " Challenger " 
from the North Pacific and South Polar seas respectively, but differ from 
all other species, and indeed from all other Pennatulida yet described. 
In possessing pinnated tentacles the zooids of U. gracilis stand absolutely 
alone. 

I have pointed out above, when discussing the nature of the zooids of P. 
phosphorea, that zooids must be considered as abortive polyps arrested in an 
early stage of development. 

It becomes now an interesting inquiry how this unitentacular condition of 
the zooids of Umbellula arose. So far as is at present known, the earliest rudi- 
ments of all eight tentacles arise simultaneously in the Pennatulid polyps. I 
have described this above in the case of the asexually formed polyps of Pennatula 

, * Kolliker, Zool. Chall. Exp., part ii. 1880, pp. 21-24. 



PENNATULIDA DREDGED BY H.M.S. "TRITON." 147 

and Virgularia, and Wilson ""' has recently shown that the same applies to the 
sexually produced young of Renilla. It appears, therefore, that the unitenta- 
cular condition of the Umbellula zooid is not a repetition of any stage occurring 
in the ontogeny of the normal Pennatulid polyp. It is, however, just possible 
that such a stage once existed in the phylogeny of the group, but has dropped 
out of its ontogeny. So far as is known, a unitentacular condition does not 
obtain in the ontogeny of any Alcyonarian, though we must bear in mind that 
very few forms have as yet been studied adequately. Among Zoantharia a 
temporary unitentacular condition occurs in Actinia mesembryantliem.um,\ while 
in Cerianthus and Arachnitis four tentacles arise simultaneously, and in other 
cases all eight. 

The definite relation of the single tentacle of the Umbellula zooid to the 
plane of symmetry seems to indicate that it has some morphological signi- 
ficance, though at present we have not evidence to determine what that 
significance is. I would, in conclusion, direct attention to the remarkable 
condition of the polyps in Scytalium tentaculatum, K6ll.,t one of the " Chal- 
lenger " species, in which each polyp has but a single tentacle, as showing that 
a unitentacular condition may be more widely spread than is at present 
suspected. 

Our knowledge of the genus Umbellula has been very greatly increased of 
late years. Two specimens taken off the coast of Greenland in 1752, and very 
imperfectly described, were for more than a century the only examples recorded. 
In 1871 Lindahl obtained two specimens, one in Baffin's Bay in 410 fathoms, 
and the other at the entrance to the Omenakfjord, in N. Greenland, at a depth 
of 122 fathoms. An Umbellula was also obtained by Nordenskiold in the 
Kara Sea, to the east of Novaya Zemlya, during the " Yega " expedition. 

The " Challenger " expedition added enormously to our knowledge of this 
genus, no less than seven new species being obtained from widely different 
parts of the world. Concerning the geographical distribution of this genus 
Kolliker says: — "After having known for more than a century only one 
locality, the North Polar Sea, near the coast of Greenland, we have now learned 
that this form is far and widely distributed. Umbellula' have now been 
obtained from the North Atlantic Ocean (between Portugal and Madeira); 
from the North Polar Sea, coast of Greenland; from the Atlantic Ocean, under 
the Equator, between Africa and America, and from the west coast of Africa, 
north of Sierra Leone (Stud.) ; from the South African Sea, west of Kerguelen 
Island ; from the South Polar Sea ; from the coasts of New Guinea and of 

* Wilson, " The Development of Renilla," Proc. Roy. Soc, 1882. 

f -Lacaze-Duthiers, " Developpement des Coralliaires," Archives de Zoologie experimentale et 
generale, vol. i. 1872, and vol. ii. 1873. 

% Kolliker, Zool. Chall. Exp., part ii., 1880, pp. 10, 11, and pi. iii. fig. 12, pi. iv. fig. 13. 



148 



DR A. MILNES MARSHALL ON THE 



Japan ; and from the middle of the North Pacific Ocean. Umbellula has, 
therefore, of all genera of Pennatulida, the widest distribution. "* 

The " Triton " specimen makes a very interesting addition both to the list 
of species of Umbellula and to the localities in which it has been found. 

The measurements of the sole specimen of Umbellula gracilis yet known are 
as follows : — 



Total length, . 






290 mm 


Length of rachis (dilated part), 






26 


Length of polyp-bearing part of rachis, 






18 


Width of rachis at widest part, 






6 


Thickness, . 






5 


Length of terminal dilatation of stalk, 






35 


Diameter, .... 






3-2 


Diameter of stalk (middle of length), 






07 


„ stem, 






0-5 


„ stem (widest part), 






0-9 


Number of polyps, . 






13 


Length of polyp (shortest), . 






15 


body, 






7-5 


„ tentacle, . 






7-5 


Length of polyp (largest), 






26 


body, 






13 


„ tentacle, . 






13 


Diameter of polyp, base, 






5 


„ just below tentacles, 






2-8 


Length of zooid, largest, 




• 


1-8 


Length of tentacle of zooid, largest, . 






1-3 



General Observations. 



Geographical Disti 'ibution . 

Horizontal Distribution. — The most noteworthy point is the great abundance 
and variety of specimens dredged at one particular locality, — Station 11. At 
this place there were obtained, from a depth of 555 fathoms, nineteen specimens 
of Pennatula phosphorea var. aculeata; three specimens of Virgularia tuber- 
culata, a new species ; one specimen of Diibenia dbyssicola var. smaragdina, a 
form hitherto found only off the Norwegian and Swedish coasts ; thirty speci- 
mens of Kophobelemnon stelliferum var. dura ; and one specimen of Umbellula 
gracilis, a new species ; i.e., example of five out of the fourteen known families 
of Pennatulida, of three distinct subsections, and two of the four sections of 
the order were obtained at this one spot. 

; * Kolliker, Zool. Cliall. Exp., part ii. 1880, p. 37. 



PENNATULIDA DREDGED BY H.M.S. " TRITON." 149 

This extraordinary profusion mark the locality as a very exceptional one. 
At each of the other stations only single species were obtained. 

Vertical Distribution. — The " Triton " observations have increased the ver- 
tical range of Pennatula phosphorea to 555 fathoms, its previously recorded 
limit being 340 fathoms ; of Diibenia abyssicola, from 120 to 555 fathoms ; of 
Kophobelemnon stelliferum v. durum, from 300 to 640 fathoms ; and have added 
a new deep water Virgularia, V. tuberculata, extending to 555 fathoms, to the 
sole one previously known, V. bromleyi. 

These results, so far as they go, do not lend any very material support to 
Kolliker's conclusion, that " the simpler forms of Pennatulida, especially those 
with sessile polyps, inhabit great depths.""" 

Kolliker ranks among primitive forms of Pennatulida the Umbettulidw, 
which are an essentially deep water family, seven out of the twelve known 
species being found below 1000 fathoms and five below 1800 fathoms, and cites 
this distribution in evidence of the view that the lower forms of Pennatulida 
are, as a rule, deep water forms. 

Umbellula appears to me, however, to be not a primitive form but a highly 
modified one. This is shown by the great length of the non-polypiferous as 
compared with the polyp-bearing part of the colony, i.e., the great prepon- 
derance of the purely colonial portion ; by the great difference between the 
polyps and the zooids ; by the extreme differentiation of some of the zooids ; 
and, above all, by the polymorphism of the zooids themselves, an almost unique 
condition among Pennatulids. In all these respects Umbellula is far less pri- 
mitive than Funiculina, which is essentially a shallow water form, attaining its 
maximum of development at about 30 fathoms depth. 

A point of considerable interest concerns the influence of increase in depth on 
the structure and habits of Pennatulids. On this point but little can be said at 
present for want of sufficient evidence. 

We have seen above that some of the deep water forms (below 500 fathoms) 
have much thicker body walls and layers, and more numerous spicules, than 
those from less depths. If we compare different genera together there would 
appear to be no relation whatever between depth of water and development of 
spicules ; thus Umbellula gracilis and Virgularia tuberculata from 555 fathoms 
have no spicules at all ; while P. phosphorea and K. stelliferum, brought up in 
the same dredge with the preceding species, have exceptionally large and 
numerous spicules. If, however, we confine ourselves to one species, we seem 
to find such a relation ; thus the specimens of Pennatula phosphorea from below 
500 fathoms have very much thicker walls, and larger and more abundant 
spicules, than those from 20 to 40 fathoms. In this case we have strong reason 

* Kolliker, Zool. Chall. Exp., part ii. 1880, p. 39. 



150 



DR A. MILNES MARSHALL ON THE 



for thinking, from the small size and somewhat stunted appearance of the deep 
water specimens, that the species is typically a shallow water one, and it is very 
possible that the increase in development of spicules is due directly to the 
change of environment. 

All the specimens of Kophobelemnon and also those of Pennatula obtained 
below 500 fathoms contain large quantities of sand mixed with Foraminifera 
shells, both in the polyp cavities and in the tentacular cavities, and also 
encrusting the exterior. The specimens of Umbellularia, Diibenia, and Virgu- 
laria brought up at the same time are, however, perfectly clean and free from 
sand. Whether this indicates difference in habits or is merely accidental, I 
have no means of ascertaining ; the specimens of Pennatula from shallow 
water have no sand in the polyp cavities, or but very little. 

Morphology. — The chief points of morphological interest on which light is 
thrown by the " Triton " specimens appear to concern the structure of the 
zooids of Pennatula and Unibellula ; and the relations of the plane of symmetry 
of the polyps established in Pennatula, Kophobelemnon, and Unibellula. 



DESCRIPTION OF THE FIGURES ON PLATES XXL— XXV. 



All the figures were drawn with the camera. -Figures 8, 28, and 33 are not taken from 
single sections, but are constructed from a number of separate camera drawings of the several 
parts shown. The numbers beneath the figures indicate in diameters the magnifying power 
employed in each case. 



Alphabetical List 

a, rachis. 

b, stalk. 

c, stem. 

d, polyp. 

dc, main dorsal canal of rachis. 
dl, leaf. 

e, zooid. 
/, large zooid. 
y, body cavity of polyp. 
h, body cavity of zooid. 
i, spicule. 
h, spicular plate. 
I, calyx process. 
/', cavity of calyx process. 
Ic, main lateral canal of rachis. 
Im, longitudinal muscles of rachis and stalk. 
m, mescutery or septum. 



of References. 

n, mouth. 

o, ovum. 

o, germinal cell or primitive ovum. 

p, long mesenterial filament. 

r, cilia of siphonoglyphe. 

rm, retractor muscle of polyp. 

s, stomodajum. 

t, tentacle. 

t', cavity of tentacle. 

u, pinnule of tentacle. 

v, spermatosphere. 

vc, main ventral canal of rachis. 

w, ectoderm. 

x, mesoderm. 

x', nutrient canals of m esoderm. 

y, end o derm. 



PENNATTJLIDA DREDGED BY H.M.S. "TRITON." 151 



Plate XXI. 

Fig. 1. — Virgularia tuherculata ; ventral surface, x 3. 

Fig. 2. — Virgularia tuherculata; portion of racbis, ventral surface, showing arrangement of 
polyps in groups of threes ; also the tubercular calyx processes and the varying 
conditions of the calyx during retraction of the polyp, x 17. 

Fig. 3. — Virgularia tuherculata ; two spermatospheres from lower part of racbis of the speci- 
men shown in fig. 1. x 70. 

Fig. 4. — Pennatula phosphorea var. aculeata; from right side. Shows characteristic shape of 
leaves, also both small and large zooids. x 2. 

Fig. 5. — Pennatula phosphorea var. aculeata ; transverse section of racbis with one entire leaf 
and the base of the corresponding one of the other side. Shows shape of leaf ; 
shape and arrangement of zooids both large and small ; great thickness of wall of 
rachis, and small size of its main canals, x 4. 

Fig. 6. — Pennatula phosphorea ; transverse section of rachis with entire leaf of normal form, for 
comparison with fig. 5. Shows great width of leaf, absence of large zooids, thinness 
of walls of rachis, and large size of main canals, x 4. 

Fig. 7. — Pennatula phosphorea var. aculeata ; lower end of rachis from left side. Shows stages 
in development of polyps, and especially the simultaneous appearance of the 
calyx processes and of the tentacles ; also the primitive independence of the 
polyps of one another. X 17. 

Plate XXII. 

Illustrating the anatomy of the large ventral zooids of Pennatula phosphorea var. aculeata. 

The reference letter t l in the figures on this plate should be l\ 

Fig. 8. — Longitudinal section of large ventral ?,ooid and of the part of the rachis from which 

it arises. Shows structure of large zooid and of one of the small zooids. x 50. 
Fig. 9. — Transverse section of a calyx process of a polyp, for comparison with the succeeding 

figure, x 150. 
Figs. 10 to 16. — Transverse sections through one of the large ventral zooids at various parts of 

its height, fig. 10 being close to the apex and fig. 16 at the base of attachment to 

the rachis. x 150. 
Fig. 10. — Through upper end of zooid, showing one calycular cavity. 
Fig. 11. — Lower down ; shows two calycular cavities. 
Fig. 12. — Lower down still ; shows three calycular cavities. 
Fig. 13. — Through upper part of mouth ; shows long cilia of siphonoglyphe. 
Fig. 14. — Through lower part of mouth ; shows five calycular cavities. 
Fig. 15. — Through stomodpeum about the middle of its length. Shows eight septa and septal 

chambers. 
Fig. 16. — Through lower part of polyp cavity, showing the two mesenterial filaments, and the 

remains of the other six septa. 

Plate XXIII. 



Fig. 17. — Diihenia abyssicola var. smaragdina. Ventral surface, x 3. 

Fig. 18. — Dubenia abyssicola var. smaragdina. Portion of rachis from left side. Shows 

arrangement of polyps in pairs, each pair embraced at base by a fan-shaped spicular 

plate, x 17. 
VOL. XXXII. PART I. 2 B 



L52 DB A. MILNE3 MARSHALL ON" THE PENNATULIDA, ETC. 

Fig. i'.). —Dubenia abyssicola var. smaragdina. Portion of rachis from dorsal surface. Shows 

arrangement of polyps and zooids. x 17. 
Fig. 20. — Dtibenia abyssicola var. smaragdina. Tentacle of polyp, showing rib of calcareous 

spicules, x 70. 
Fig. 21. — Dubnn.it abyssicola var. smaragdina, one of large spicules of spicular plate, x 55. 
Fig. 22. — Funiculina quadrangularis. Portion of rachis of young specimen from left side. 

Shows shape of polyp in state of extreme contraction; also extension of spicules 

down whole length of polyps and on to rachis. x 7. 

Plate XXIV. 
Kophohelemnon stellifcrum var. durum. 

Fig. 23. — Whole specimen, dorsal surface ; showing typical arrangement of polyps, x 2. 

Fig. 24. — Tentacle of polyp; showing rib of calcareous spicules extending whole length of 
tentacle and along pinnules, x 20. 

Fig. 25. — Transverse section of tentacle, showing tentacular cavity and extension into pinnules, 
also arrangement and shape of spicules, x 70. 

Fig. 26. — Two large spicules from spicular rib of tentacle, x 55. 

Fig. 27. — Transverse section of stalk ; showing arrangement of spicules and muscles ; als^ 
shape of stem and of main longitudinal canals, x 30. 

Fig. 28. — Transverse section of rachis passing through three polyps at different portions of 
their length. The left-hand polyp is cut horizontally (cf. fig. 23), and shows stomo- 
daeum, mouth, and tentacles ; the right-hand polyp is cut transversely through the 
lower portion of the stomodaeum, and shows arrangement of retractor muscles and 
position of plane of symmetry of polyp ; the third or dorsal polyp is cut trans- 
versely at a still lower leyel, and shows the two mesenterial filaments and a 
number of ova. The section also shows several zooids and the shape and position 
of the stem aud of the main ventral canal, x 30. 



Plate XXV. 

Umbellula gracilis. 

-Whole specimen; dorsal surface, x 1. 

-Eachis ; ventral surface. Shows arrangement of polyps and zooids. x 2. 
-Tentacle of polyp ; shows alternation of large and small pinnules, x 10. 
-Apex of rachis; ventral surface. Shows shape and arrangement of lar^e zooids 
with pinnate tentacles, x 14. 
Fig. 33. — Longitudinal section of one of the large zooids; shows the tentacle with its pinnules 

mouth, stomod;eum, mesenterial filament, &c. x 55. 
Fig. 34. — Section of septum bearing ova, and of the part of the body wall of the polyp from 
which the septum arises. Shows also the disposition of the retractor muscle, 
x 70. 
Fig. 35. — Section of ovigerous septum close to its free edge, showing various stages in the 
early development of the ova. x 470. 



Fig. 


29. 


Fi". 


30 


Fig. 


31 


Fig. 


32 



Soc. Edm 1 



Vol XXXII, Plate XXI. 



Fig.l 

X 3 







VIRGULARIA. PENNATULA 



"F.H.iix,La.'Ea.t 



Vol XXXII, Plate XXII. 




AM Marshall M iliut 



FHutri ( LilFEd.n' 



PENNATULA. 



■ans Roy. Soc. Edin r 



Fig. 17. 

X 3 



Fig. 18. 



X 17 




Fig. 19. 

X 17 




Vol.XXXll, PI. XXIII. 
X 55 






a— I 



V! 



?t ■-- 



/#-* 



DUBENIA. FUNICULINA 



Fig. 22. 



X 7 





T KuOi,li!h , T.am r 



r&0 ■ W, 






'rans.Roy. Soc. Edin 1 



Fig. 23 

X 2 



Vol. XXXII, PL XXIV. 




IHufl 1 ,Litk'-EJ™ 1 



KOPHOBELEMNON 



Vol. XXXII, Plate XXV. 




I 



■ 




^Marshall del ad nat. 



^S^^^^P^ 



TH.ia.LiOi'Eam 1 



UMBELLULA 



( 153 ) 



IX. — Aster oidea dredged in the Faeroe Channel during the Cruise of If. M.S. 
"Triton" in August 1882. By W. Percy Sladen, F.L.S., F.G.S. 
Communicated by John Murray, F.R.S.E. (Plate XXVI.) 

(Read 16tli July 1883. ) 

The star-fishes recorded in the. present communication were dredged by Mr 
John Murray during the cruise of H.M.S. " Triton " (under the command of 
Staff-Commander Tizard, RK), whilst investigating the nature of the Wyville- 
Thomson Ridge and the adjacent portions of the Faeroe Channel. All the 
forms, excepting these from Station 3, were obtained from deep water, and the 
collection, as a whole, is both rich and interesting. One species and two well- 
marked varieties have not hitherto been described, and two other species have 
only been found once previously. The series consequently forms a valuable 
supplement to the collections made during the cruises of H.M.S. "Porcupine" 
and the " Knight Errant," and is an important addition to our knowledge of the 
fauna of this region of the Atlantic. I propose to reserve any remarks upon 
the general character of the asterid fauna of the Faeroe Channel until treating 
of the collections obtained during the "Porcupine" and "Lightning" cruises. 

I am indebted to Mr Murray for his kindness in placing this collection in 
my hands. 

I. List of the Species Collected. 

1. Pteraster militaris (O. F. Miiller), Miiller and Troschel. 

Station 2. August 5, 1882. Lat. 59° 37' 30" N., long. 6° 49' W. 
Depth, 530 fathoms ; bottom temperature, 46°2 Fahr. 

2. Pteraster militaris, var. prolata, no v. (Plate XXVI. fig. 1.) 

Station 9. August 23, 1882. Lat. 60° 5' N., long. 6° 21' W. 
Depth, 608 fathoms ; bottom temperature, 30° Fahr. 

This is a remarkable form, differing greatly in general appearance from the 

| normal type of P. militaris ; and although it accords in the main with the 

diagnostic formula of that species, the majority of the characters differ more or 

less in degree. It is not improbable that a series of examples might ultimately 

warrant its being ranked as a distinct species ; but for the present I prefer to 

vol. xxxii. part i. 2 c 



(54 MR W. PERCY SLADEN ON THE 

place the solitary specimen as a variety of P. militaris until further material is 
available — a course which is sufficient to identify the form, and at the same time 
indicate the nearest specific affinities. 

The variety is characterised by the following points : — The great length and 
narrowness of the rays ; R > 3 r ; R = 58 to 60 mm., r= 18 mm. ; breadth of a ray 
at the base, 18 to 22 mm. extreme measure. The dorsal paxillse appear usually 
to have one of their spinelets much more robust than the two or three com- 
panion spinelets, which are remarkably fine and delicate, and the tips of the 
spinelets can scarcely be said to protrude through the supradorsal membrane, 
notwithstanding that this latter is placed rather loosely upon them, and much 
wrinkled. Two or three lineal series of paxillae are more or less clearly distin- 
guishable along the sides of the rays. On the actinal surface the segmental 
apertures are remarkably large, and the aperture-papillae are much broader and 
more robust at their proximal portion than in P. militaris. In the ambulacral 
spines the three inner spines of each transverse comb form a line oblique to the 
furrow, the comb being curved aborally at the margin of the furrow, and the 
position of these spines upon the adambulacral plate being also oblique in rela- 
tion to the plane of the ray. The actino-lateral spines are very short, and the 
outer portion of the web which proceeds from the outermost ambulacral spine, 
i.e., the membranous continuation of the transverse comb upon the actinal 
membrane, is much more prominent than in the typical form of the species, and 
extends up to the margin of the lateral fringe. Although these differences may 
appear insignificant verbally, they produce when combined a striking facies, the 
characters of which can hardly be explained, as being simply the modifications 
of the normal form consequent on the conditions of a deep water habitat, since 
the example of P. militaris from 530 fathoms (Station 2), recorded above, differs 
in no way from the normal form. 

3. Archaster tenuispinus (Duben and Koren), Sars. 

Station 9. August 23, 1882. Lat. 60° 5' N., long. 6° 21' W. 
Depth, 608 fathoms ; bottom temperature, 30° Fahr. 

4. Archaster bi/rons, Wyville Thomson. 

Station 10. August 24, 1882. Lat. 59° 40' N., long. 7° 21' W. 
Depth, 516 fathoms ; bottom temperature, 46° Fahr. 
Station 11. August 28, 1882. Lat, 59° 29' N., long. 7° 13' W. 
Depth, 555 fathoms ; bottom temperature, 45° 5 Fahr. 

5. Astropecten Andromeda, Midler and Troschel. 

Station 10. August 24, 1882. Lat. 59° 40' N., long. 7° 21' W. 
Depth, 516 fathoms ; bottom temperature, 46° Fahr. 



ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. "TRITON." 155 

Station 11. August 28, 1882. Lat. 59° 29' N., long. 7° 13' W. 
Depth, 555 fathoms; bottom temperature, 45 0, 5 Fahr. 

The propriety of retaining this form in the genus Astropecten appears to be 
questionable. I propose to reserve the discussion of the subject until dealing 
with some allied forms obtained by the " Challenger " expedition. 

6. Luidia ciliaris, Philippi. 

Station 3. August 8, 1882. Lat. 69° 39' 30" N., long. 90° 6' W. 
Depth, 87 fathoms; bottom temperature, 49° 5 Fahr. 

I consider this form separate from L. Sarsii, D. and K. Both species were 
comprised in Forbes' L. fragilissima. I regard L. Savignyi, Audouin, distinct 
from either. 

Rhegaster, gen. nov. 

Marginal contour subpentagonal ; rays slightly produced. Abactinal sur- 
face more or less convex, actinal flat. The whole body covered with mem- 
brane, beset with crowded spinelets. 

Abactinal skeleton composed of irregular plates, crowded and subimbricated 
in places, which leave small irregularly disposed meshes. The whole skeleton 
is hidden in a thick membrane, and furnished with a compact covering of 
small, uniform, crowded spinelets. Papulae small, numerous, isolated, irregu- 
larly distributed over the whole area. Infero-marginal plates large, forming 
the margin of the test. Supero-marginal plates superficially invisible, concealed 
in the dorsal membrane. Actinal interradial areas with large subregular plates, 
hidden by a superficial membrane, with small crowded spinelets. 

Adambulacral plates broader than long. Ambulacral spines short and 
thickly invested with membrane, forming a regular furrow-series and several 
subregular longitudinal rows externally. Ambulacral sucker-feet in simple pairs, 
with small sucker-disk. 

Madreporiform body small, midway between margin and apex. Anus sub- 
central. No peclicellarige. 

This genus comes within the scope of the family Asterinidce as defined by 
Dr Viguier, and appears to be well distinguished from the other genera of the 
group. In addition to the species now described, I include in the genus the 
interesting form named by Dr Stuxberg* Solaster tumidus, but which has more 
recently been referred to the genus Asterina by Drs Danielssen and KoREN.t 
The latter naturalists have given an admirable description, and two detail 

* Ofversigt af Kongl. Vet.-Akad. Forhandl, Arg. 35, 1878 (1879), No. 3, p. 31, pi. vi. 
f Nyt Mag. f. Naturvidensk., Bd. xxvi. hffc. 2, p. 182, pis. i. and ii. figs. 6-10. 



156 MR W. PERCY SLADEN ON THE 

figures of specimens dredged during the Norwegian North Atlantic Expedition, 
and a well-marked variety (var. tuberculata, D. and K.) is also defined. Daniel- 
ssen and Koren state that they place the S. tumidus provisionally as an 
Asterina, and mention at the same time a number of important points wherein 
the form differs from that genus. The determination appears to have been 
published with cautious hesitation, and I feel bound to express regret that the 
circumstance of the discovery of the new species should force upon me the 
undesired course of forestalling the Norwegian savants in the establishment of 
a genus for the reception of a form upon which they have bestowed such care- 
ful study. 

Through the kindness of Professor Loven, I had the privilege of examining 
Dr Stuxberg's type specimens when in Stockholm last autumn, and I am able 
to confirm the opinion of Drs Danielssen and Koren in regarding the original 
reference of the form to Solaster as altogether untenable. 



7. Rhegaster Marrayi, n. sp. (Plate XXVI. figs. 2-7.) 

Station 5. August 10, 1882. Lat. 60° 11' to 60° 20' N., long. 8° 15' to 

8° 8' W. 
Depth, 433 to 285 fathoms ; bottom temperature, 43°*5 to 40° '8 Fahr. 

Marginal contour subpentagonal, rays slightly produced; the lesser radius 
in the proportion of 77 per cent, or as 5 : 65. R=143 mm., r=ll mm. 

Interbrachial angles somewhat indented at the median interradial line, from 
whence the contour curves outward faintly, consequent on a slightly tumid swell- 
ing at the base of the ray, and is then gracefully incurved towards the tip, which 
is obtuse and rounded. Abactinal area high and convex over the disk, sloping 
down regularly to the extremity of the rays, the height at the centre of the disk 
being 11*75 mm. A feeble sulcus or depression is present on the outer part of 
the median interradial line, which emphasises the tumid character of the base 
of the rays. Actinal surface more or less flat, excepting that the rays are 
slightly turned up at their extremity, and that a rather sharp depression occurs 
in the interbrachial areas along the inner part of the median interradial line, 
behind the mouth-plates. 

Dorsal area covered with short, delicate spinelets, all of uniform length and 
size, their lower portion being apparently sunken in membrane. The spinelets 
stand perpendicular and are closely placed, presenting to the naked eye the 
appearance of a fine and uniformly granular surface. When magnified the 
spines are seen to be slightly expanded or flaring outwardly, and to be com- 
posed of many rods or lamellaj, with the extremity of each individual lamella 
terminating in a short thorn-like point. 



ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. "TRITON." 157 

The spinous dorsal area is punctured with numerous small but conspicuous 
pores, which are irregularly distributed at small but unequal distances apart 
over the whole area, excepting the extremities of the rays and a narrow band 
along the median interradial line ; towards the margin the apertures are 
smaller, wider apart, and less frequent. Through these apertures the papulae 
are protruded, and under magnification a small but definite circlet of the dorsal 
membrane surrounding the puncture of the papula, and unencroached upon by 
spinelets, may be seen. No grouping of the dorsal spinelets occurs, which in 
any way indicates the outlines. of the underlying plates of the abactinal floor ; 
and the only break in this perfectly uniform covering consists of a number of 
most minute channel-lines, which run irregularly here and there amongst the 
spinelets, the only one of these maintained with any regularity being a long 
straight channel, similar in breadth to all the others, extending along the 
median interradial line. The anal aperture is subcentral and distinct, and is 
surrounded by slightly larger spinelets. The madreporiform body is very 
small, round, and with numerous striae. It is situated rather nearer to the 
margin than midway to the centre of the disk, and the surrounding portion of 
the test is slightly prominent. 

Actinal interradial areas extensive, and with their outer margin conspicu- 
ously festooned by the infero-marginal plates. Infero-marginal plates eight to 
nine in number from the interbrachial line to the tip of the ray ; the contour of 
their outer margin is rounded, and bears a group of eight to twelve spinelets, 
rather larger and more robust than those of the dorsal area above described. 
The plates are entirely covered with spinelets — the part which falls in the 
side of the ray with spinelets similar to those on the dorsal area, and the 
ventral portion with spines similar to those on the ventral area. When 
the starfish is viewed in profile, the marginal plates are seen to be clearly 
marked out by vertical furrows as well as by their prominent tumidity ; 
but the junction of the infero-marginal with the supero-marginal plates, or 
indeed the presence of these latter at all, is indiscernible to superficial obser- 
vation. Seen on the actinal side, the marginal plates are clearly defined by 
well-marked channels or furrows, and these run in oblique lines from the 
margin up to the adambulacral plates. The furrows are almost regularly 
parallel, hence the areas or columns they define are of nearly uniform 
breadth throughout. Consequent on their diagonal direction, a triangular 
space occurs in the median interbrachial line in the inner portion of the area, 
which is not conformable to the arrangement above described, the channels 
which traverse it converging towards the apex of the triangular space, a short 
distance removed from the margin of the disk. The whole ventral area is 
covered with small, almost spicular, spinelets, which are short, sharply pointed, 
and with their bases buried in membrane. The spinelets are all nearly uniform 



158 MR W PERCY SLADEN ON THE 

in size, rather widely spaced, and are directed outward, almost horizontally, 
the angle at which they stand to the actinal surface being very small. 

Ambulacra! furrows narrow and almost uniform in breadth throughout. 
Adambulacral plates broader than long, bearing from five to eight spines. 
The ambulacral spines form a regular inner or furrow series, which arches over 
and almost conceals the ambulacral sucker-feet, and three sub-regular outer 
rows more or less clearly defined. The following is the arrangement of the 
spinelets on the plates : — Of the inner or furrow series there are two on each 
plate, which stand side by side and slightly oblique, especially towards the 
end of the ray. These two spines are regular throughout the ray, and are of 
equal size, short, compressed, lanceolate, tapering to a sharp point, and invested 
in membrane, which adds to the apparent breadth of their base. The outer 
spines are subject to a considerable amount of variation, both in number and 
position. Three only may be present, each placed behind the other, external 
to the furrow spines, forming a transverse series on the adambulacral plate, or 
one, two, or even all three of these spines may be reduplified — the companion 
spine usually standing rather oblique. These variations do not appear to be 
dependent on position in the ray, but may occur in any part. All the outer 
spines are of uniform size, cylindro-conical in shape, rather obtusely pointed, 
and covered with membrane. 

Mouth-plates form a triangular mouth-angle, not prominent or protuberant 
superficially, and perfectly conformable with the triangular outline of the inter- 
radial area. The mouth-aperture is completely closed, and the arrangement of 
the armature of the mouth-plate is suggestive of that in certain Goniasteridce. 
The mouth-spines are short, robust, and stand perpendicular. One odd spine 
is placed at the extreme angle, at the junction of the two plates of a mouth- 
angle, and five similar spines, all closely placed, occupy the free or furrow 
margin of the plate, decreasing in size as they recede from the mouth ; the odd 
spine being the largest, the next three slightly smaller, and the two outer ones 
much smaller. All the spines are cylindrical, slightly taper, and obtusely 
rounded at the tip. Upon the surface of the plates, and on a line with the 
two small outer mouth-spines, stand two short secondary or superficial mouth- 
spines, one on each plate, very robust at the base, conical and pointed ; and, 
further outward again, a second, but much smaller, spine behind each of the 
secondary mouth-spines ; this small pair perhaps belonging to the adambu- 
lacral plate adjacent to the mouth -plates. A single minute spinelet, situate 
on the median or sutural line of the mouth-plates, stands midway between 
each of the pairs of secondary mouth-spines ; and no other spines of any 
description are present on the mouth-plates. 

Remarks. — The form above described is nearly allied to Rhegaster tumidm 
(Stuxberg, sp.). The following appear to be the chief points of difference : — 



ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. " TRITON." 159 

The length of the ray is much less in the new species, the radial proportions 
being for R. Murrayi, R, = 1'3?*, and for R. tumidus R = 19r, in specimens of 
the same size. The rays are consequently much less defined, and are more 
widely expanded at the base. In R. Murrayi the marginal contour is dis- 
tinctly festooned by the infero-marginal plates, and each of these bears a group 
of enlarged spinelets, neither of the characters being present in R. tumidus. 
The ambulacral spines appear to be more numerous in the new form, the arma- 
ture of the mouth-plates somewhat different, the distribution of papulae more 
numerous on the dorsal surface, and the character of the spinelets, both on 
the abactinal and actinal areas, more simple. 

I have great pleasure in associating this interesting species with the name 
of Mr John Mukray, whose zealous labours in connection with deep-sea 
dredging are well known. 

8. Mimasier Tizardi, Sladen. 

Station 10. August 24, 1882. Lat. 59° 40' N., long. 7° 21' W. 
Depth, 516 fathoms ; bottom temperature, 46° Fahr. 

Station 11. August 28, 1882. Lat. 59° 29' K, long. 7° 13' W. 
Depth, 555 fathoms ; bottom temperature, 45°5 Fahr. 

9. Hippasteria plana (Linck), Gray. 

Station 3. August 8, 1882. Lat. 60° 39' 30" N., long. 9° 6' W. 
Depth, 87 fathoms; bottom temperature, 49° 5 Fahr. 

10. CribreUa oculata (Linck), Forbes. (Plate XXVI. fig. 8.) 

Station 1. August 4, 1882. Lat. 59° 51' 30" N., long. 6° 21' W. 
Depth, 240 fathoms ; bottom temperature, 47° "6 Fahr. 

Station 10. August 24, 1882. Lat. 59° 40' N., long. 7° 21' W. 
Depth, 516 fathoms ; bottom temperature, 46° Fahr. 

Station 11. August 28, 1882. Lat. 59° 29' N., long. 7° 13' W. 
Depth, 555 fathoms ; bottom temperature, 45°*5 Fahr. 

The specimens from Stations 10 and 11 have an abnormal appearance, even 
for this variable species, probably, consequent on their deep-water habitat. 
The variation is characterised by the comparative smallness of the disk and the 
greater length and narrowness of the rays, which are subcylindrical and almost 
uniform in breadth throughout, especially in the small examples where the 
expansion at the base is very slight. The single example from Station 11 
measures R = 39 mm., r = 5 mm., breadth of ray at the base 575 mm. The 
spinelets of the abactinal area are very small, and rather more widely spaced 
than in the normal form. They are conically pointed, and have the appearance 



160 MR W. PERCY SLADEN ON THE 

of being rooted in membrane and rather thickly invested at their base, which 
gives the spine-groups a larger and somewhat more expanded character than 
usual in shallow water specimens. The three examples from Station 10 are 
much smaller, and their spinulation is very minute and scanty, seldom more 
than two to four spinelets being present in a group. The effect of this is 
perhaps most striking in the armature of the adambulacral plates, where the 
group of spines external to the furrow-series becomes abnormally small and 
insignificant. The comparative length of the ray and its almost uniform 
breadth is very conspicuous in conrparison with small specimens of similar size 
of the ordinary form, in which the ray is proportionally shorter in the young 
stage than in the adult. The colour in alcohol of the specimens under notice is 
a dirty greyish- brow 7 n. 

Considering the known variability of the species, I do not at present feel 
justified in doing more than placing on record the character of the variation 
above noted. If a larger supply of material should ultimately necessitate the 
nominal recognition of this form as a deep-sea variety, it might appropriately 
be called cylindrella. 

11. Zoroaster fulg ens, Wyville Thomson. (Plate XXVI. figs. 9-11.) 

(Zoroaster fulgens, Wyv. Thorns. (1873), The Depths of the Sea, p. 154, fig. 26.) 

Station 11. August 28, 1882. Lat. 59° 29' N., long. 7° 13' W. 
Depth, 555 fathoms ; bottom temperature, 45°'5 Fabr. A young 

example. 
Station 13. August 31, 1882. Lat. 59° 51' 2" N., long. 8° 18' W. 
Depth, 570 fathoms ; bottom temperature, 45°'7 Fahr. 

A brief description and a woodcut of this handsome starfish were given by 
Sir Wyville Thomson in the work cited above. As no detailed description of 
the species has yet been published, the following may not be unacceptable : — 

Rays five. 11 = 125 to 130 mm.; r=14 to 15 mm. 

Rays very long, narrow, subcylindrical, and tapering throughout to a finely 
pointed extremity ; arched on the abactinal surface, and tumid on the actinal 
surface on either side of the furrow, which is deeply sunken. Interbrachial 
angles acute. Breadth of a ray at the base 17 mm. 

The disk is rather higher than the. rays and slightly tumid. The calcareous 
skeleton of the whole test is formed of suboval or subhexagonal plates, disposed 
in perfectly regular longitudinal and transverse series. The following is the 
arrangement they present. Surrounding a dorso-central and five small radially 
placed plates arc five large plates interradial in position; and outside and 
alternating with these are five similar but rather smaller radially placed plates.* 

It will Ik: noted that these plates represent in a remarkable manner the dorso-central, the under 
basals, the basals, and the radials respectively of the crinoid calyx. 



ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. "TRITON." 161 

Outward from each of the radial plates proceeds a longitudinal series of plates 
which extends along the median dorsal line of the ray, each plate regular in 
form (subhexagonal) and touching or slightly imbricating upon its next serial 
companion. On either side of this median line of plates is a parallel line of 
smaller plates, and these are succeeded by a line or series of plates nearly equal 
in size to those of the median line ; the outer of these lines of plates standing 
on the rounding which separates the dorsal and lateral areas of the ray. 
Between this dorso-lateral line and the adambulacral plates are five longi- 
tudinal and parallel series of plates, the three upper rows forming the sides of 
the ray and the two lower being on the tumid actinal surface. The plates of 
the two upper rows of the lateral series are broader than those in the three 
lower series. The longitudinal arrangement of all the series is perfectly 
regular, and the plates diminish gradually in size as they proceed outward. 
Excepting the median dorsal line, the plates of all the other rows form regular 
transverse series, as well as longitudinal. The plates of the median dorsal line 
are slightly larger than the others, and consequently do not correspond. All 
the plates are contiguous, but leave a small diamond-shaped or sub-circular 
mesh between the rounded corners of adjoining plates. This is covered with 
membrane, through which one or more small papulae proceed, and on which are 
usually borne one, or occasionally two, small forficiform pedicellarise. The 
meshes form perfectly regular longitudinal lines, and this character, as well as 
their presence, is rendered more conspicuous by the slightly tumid surface of 
the plates. The surface of all the plates is studded with a number of small, 
uniform, well-spaced miliary granules, on which are articulated very short 
ciliary spinelets thinly covered with membrane. The plates of the median 
dorsal line are sub-mammillated, rising to a small but definite tubercle in the 
middle, which gives attachment to a short, robust, conical spinelet, the sur- 
rounding portions of the plate being covered with the same small miliary 
granules and spinelets as the other plates. Isolated dorso-lateral plates are 
occasionally similarly mammilated and spined, and the large interradial plates 
on the disk are also usually thus furnished. On the plates of the three rows 
which succeed the adambulacral plates, there are usually one to three spinelets 
much longer and more robust than the accompanying miliary spinelets. These 
are naked, delicate, cylindrical, and taper to a fine extremity, and are generallv 
arranged in slightly oblique lines, with the middle spine often more forward 
and longest when three are present, near the lower margin of the plate, and 
they are directed upward and appressed to the ray. The next row on the sides 
of the ray, i.e., the fourth from the adambulacral plates, has one larger spine on 
each plate, of equal size to the afore-mentioned. The adambulacral plates are 
quite within the furrow, and are short but broad, extending far upward almost 
vertically. Each alternate plate is developed into a thin prominent ridge, 

VOL. XXXII. PART I. 2D 



162 MR W. PERCY SLADEN ON THE 

which extends far into the furrow and entirely separates neighbouring suckers, 
whilst the intermediate plates are smooth, and appear to form the true furrow- 
wall. Four ambulacral spines, which are moderately long, cylindrical, and 
slightly tapering, are placed in single file at intervals along the edge of the 
ridge, the innermost being usually the most delicate, and the outermost is 
usually the shortest. Two to five small forficiform pedicellarice are attached by 
membrane to the extremity of the delicate innermost spine. One or two small 
ciliary spines may be present on the extreme outer edge of the adambulacral 
plate, adjacent to the first row of longitudinal plates ; and two or three similar 
small spines are present in the same position at the outer edge of the non- 
prominent intermediate plates, but no spines whatever are present on the 
surface of these plates within the furrow. 

The actinostome is deeply depressed, and the mouth-plates are entirely 
within the cavity, and are not apposable. They are armed only with pointed, 
moderately robust spines similar to the larger spines on the ridges of the 
adambulacral plates. 

The madreporiform body is small and inconspicuous, and is placed external 
to one of the interradial plates. 

The anal aperture is small, distinct, surrounded by a circlet of small ciliary 
spines, and is placed at the side of the dorso-central plate, and consequently 
slightly excentric in position. 

The ambulacral sucker-feet form four rows. They are rather small, sub- 
conical, and terminated with a small but distinct fleshy sucker. 

Premature Phase.— The young form, measuring R= 11 mm. and r = 225 mm., 
has a very remarkable appearance, owing to the prominence and distinctness of 
the component plates of the skeleton. The disk is much higher than in the 
adult. The dorso-central plate is prominent, and assumes the shape of a 
rounded cone. The interradial and first radial plates are of nearly equal size, 
and are very tumid or almost semi-globular in form. The plates of the median 
dorsal line are large and distinct, occupying a large portion of the abactinal 
surface of the ray. The so-called dorso-lateral series of plates form the margin 
of the ray, and the intermediate plates are small. Between the "dorso-lateral" 
series and the adambulacral plates there are not more than two fully- developed 
longitudinal rows of plates, with a partially-developed series commencing to 
appear between the latter and the adambulacral plates. The terminal (ocular) 
plates are very large, somewhat resembling the shape of a serpent's head, and 
are armed with one or two pairs of comparatively large robust spinelets, near 
the extremity, which are directed outwards. 

The large plates of the disk and the median dorsal line have already a small 
tubercle, but only some of these bear spinelets. All the plates have a few 
widely spaced and very minute granules and microscopic ciliary spinelets. The 



ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. "TRITON." 163 

spinelets on the lower rows of plates are comparatively long and well developed. 
The character of the alternate prominent adambulacral plates is already dis- 
cernible, although not more than one or two ambulacral spinelets are present 
on each. 

The madreporiform body is outside and external to the interradial plate, and 
almost in the ravine of the interbrachial angle. The anal aperture is excentral, 
and situated between the dorso-central plate and an interradial plate, standing 
in the right posterior interradius when the madreporiform body is placed in the 
right anterior interradius. 

12. Asterias Miilleri, Sars. 

Station 5. August 10, 1882. Lat. 60° 11' to 60° 20' N., long. 8° 15' to 

8° 8' W. 
Depth, 433 to 285 fathoms ; bottom temperature, 43° -5 to 40° -8 Fahr. 



II. Station-Lists. 

The following lists show the species associated at the respective stations : — 

Station 1. August 4, 1882. Lat. 59° 51' 30" K, long. 6° 21' W. 
Depth, 240 fathoms; bottom temperature, 47 0, 6 Fahr. 
Cribretta oculata. 

Station 2. August 5, 1882. Lat. 59° 37' 30" N., long. 6° 49' W. 
Depth, 530 fathoms; bottom temperature, 46° 2 Fahr. 
Pteraster militaris. 

Station 3. August 8, 1882. Lat. 60° 39' 30" K, long. 9° 6" W. 
Depth, 87 fathoms ; bottom temperature, 49°o / Fahr. 

Hippasteria plana. 

Luidia ciliaris. 

Station 5. August 10, 1882. Lat. 60° 11' to 60° 20' N., long. 8° 15' to 8° 8' W. 
Depth, 433 to 285 fathoms ; bottom temperature, 43° 5 to 40° 8 Fahr. 

Rheg aster Murrayi. 

Asterias Miilleri. 

Station 9. August 23, 1882. Lat. 60° 5' N., long. 6° 21' W. 
Depth, 608 fathoms ; bottom temperature, 30° Fahr. 

Pteraster militaris var. prolata. 

Archaster tenuispinus. 



1(U MB W. PERCY SLADEN ON THE ASTEROIDEA, ETC. 

Station 10. August 24, 1882. Lat. 59° 40' N, long. 7° 21' W. 
Depth, 516 fathoms ; bottom temperature, 46° Fahr. 

Archaster bifrons. 

Astropecten Andromeda. 

Mimaster Tizardi. 

Cribrella oculata var. cylindrella. 

Station 11. August 28, 1882. Lat. 59° 29' N., long. 7° 13' W. 
Depth, 555 fathoms; bottom temperature, 45° *5 Fahr. 

Archaster bifrons. 

Astropecten Andromeda. 

Mimaster Tizardi. 

Cribrella oculata var. cylindrella. 

Zoroaster fulgens. 

Station 13. August 31, 1882. Lat. 59° 51' 2" N., long. 8° 18' W. 
Depth, 570 fathoms ; bottom temperature, 45° '7 Fahr. 
Zoroaster fulgens. 



DESCRIPTION OF PLATE XXVI. 

Pteraster militaris var. prolata. Abactinal aspect ; natural size. 
Rhegaster Murrayi. Abactinal aspect ; magnified 2 diameters. 
„ Actinal aspect; magnified 2 diameters. 

„ Portion of the dorsal surface ; magnified 20 diameters. 

„ One of the spines of the dorsal surface, seen in profile ; highly 

magnified. 
„ The same spine seen from above ; highly maguified. 

„ Adambulacral plates and portion of the adjacent ventral sur- 

face ; magnified .8 diameters. 
„ Mouth-plates; magnified 10 diameters. 

Cribrella oculata var. cylindrella. Abactinal aspect ; natural size. 
Zoroaster fulgens. A young example. Abactinal aspect ; magnified 3 diameters. 
„ Outline of the profile of the. same specimen. 

Fig. 11. „ Diagram of the plates of the disk, showing their correspondence 

with the crinoid calyx. The respective plates are marked as 
follows : — 

1. Dorso-central. 

2. Under Basals. 

3. Basals. 

4. Radials. 



Fig. 
Fig. 
Fig. 
Fig. 
Fig. 


1. 
2. 
3. 
4. 
5. 


Fig. 


5a. 


Fig. 


6. 


Fig. 


7. 


Fig. 
Fig. 


8. 
9. 


Fig. 


10. 




Vol UXl\ ?1 ite 



4 



WM 








1. PTERASTER MILITARIS, var. PROLATA. 
8. CRIBREUA OCULATA, var. CYLINDRELLA. 



2-7. RHEGASTER MURRAYI, 
9-11. ZOROASTER FULGENS. 



,■ i ■ i.. 



( 165 ) 



X. — On a New Species of Pentastomum (P. protelis), from the Mesentery oj 
Proteles cristatus ; with an Account of its Anatomy. By W. E. Hoyle, 
M.A. (Oxon.), M.R.C.S., Naturalist to the "Challenger" Commission. 
(Plates XXVII. and XXVIII.) 

(Read June 4, 1883.) 

For the parasites which form the subject of the present communication, I 
am indebted to my friend Professor Morrison Watson, who found them in a 
male specimen of Proteles cristatus, Sparrman, of whose myology he has since 
published an account. * Before entering upon a description of the entozoon, it 
may be allowable to say a word or two with respect to its host, which is not 
an animal of everyday occurrence. It was first described a little more than a 
century ago by SPARRMAN,t the Swedish traveller, as occurring in South Africa, 
where it is known to the farmers as the " grey jackal " ; he gave it the name 
Viverra cristata. The only point in his description of any present interest is 
that its stomach " had nothing but ants in it, or to speak more properly, the 
white termites" which might be a valuable hint for any one who had the will 
and opportunity to investigate the life history of the parasite before us. 

Since the time of Sparrman, it was erected into a separate genus by 
Geoffroy St Hilaire, and the name Proteles was chosen as expressing the fact 
that its anterior extremities were each provided with five, or the perfect 
number, of toes. It is now generally regarded as a type intermediate between 
the Hyamidae and Viverridae, its appearance when alive being strikingly like 
that of small hyama.J 

The animal dissected by Professor Watson remained some days before the 
abdomen was opened, a circumstance which affected very prejudicially the 
histological preservation of its inhabitants, and made me hesitate for some time 
as to whether it would be worth while to attempt a complete account of the 
creature's anatomy ; however, in consideration of the rarity of the specimens, it 
was resolved to make the effort, and the result has been the discovery of some 
interesting anatomical relations, although the account of the minute structure 
is in many particulars less complete than it would otherwise have been. 

* Proc. Zool. Soc. Lund , p. 579, 1882. 

t Sparrman, Andrew, M.D., A Voyage to the Cape of Good Hope, Sfc. Translated from the 
Swedish original, London, 178G, vol. ii. p. 177. 

% Flower, Proc. Zool. Soc. Land., p. 474, 1869. 

VOL. XXXII. PART I. 2 E 




1GG MR W. E. HOYLE ON" 

The Enclosing Cyst. 

The parasites, to the number of about ten, were enclosed in cysts in the 
mesentery, and their appearance is shown in the accompanying 
woodcut (fig. 1). Each is coiled into a more or less complete 
circle, and, in every case examined except one, the ventral sur- 
face formed the convexity of the curve. 
Fig. 1. General appear- The cyst itself presents nothing in its structure worthy of 
parasite. * eucy5te special note ; it consists of closely interwoven fibrils of connec- 
tive tissue, imbedded in a quite homogeneous matrix ; the wall is about O^Oo 
mm. thick, and it is more compact towards the inner than the outer surface. 

The External Appearance. 

The form of the body is (PI. XXVII. fig. 1), speaking generally, cylindrical 
in the anterior half, and slightly tapering in the posterior, until it ends in a 
blunt cone. In some specimens the last two segments presented an appear- 
ance which may be aptly described in the words used by Diesing in speaking of 
another species, "cute externa in form& prseputii"; but this was by no means 
constant. 

The head is hemispheroidal, and is followed by a smooth cylindrical portion, 
which is of very variable length ; in some cases it scarcely seems 
to exist at all, whilst in others it measures from 2 to 3*5 mm. (cf. 
PI. XXVII. fig. 1, and woodcut, fig. 2). 

This is succeeded by a number of annuli, which give the 
'face of thehead! 1 body a decidedly vermiform appearance, although, as will be 
seen in the sequel, this segmentation is scarcely at all reproduced in the internal 
organisation. 

The number of the annuli varies with the sex, and also, though to a less 
extent, with the individual ; it amounts in the males to 16 or 17, in the females 
to from 18 to 22. Each of these rings is separated by a constricted portion of 
the body, which may conveniently be termed the " interannular space"; these 
are somewhat less than the annuli, not only when measured transversely to the 
creature, but also longitudinally, except when it is very fully extended, under 
which circumstances the two sets of rings become about equal. Furthermore, 
the interannular spaces are of much weaker consistency than the annuli, as will 
be explained in treating of the internal anatomy; and in correlation with this fact, 
it is to be noticed that when the animal is coiled up, it is the interannular spaces 
which give way to allow of this, the annuli scarcely undergoing any change at 
all in breadth, but approaching each other on the concave aspect of the curve. 
On the ventral surface of the head, and about 1 mm. from its anterior 




A NEW SPECIES OF PENTASTOMUM. 167 

margin, in the middle line, can be readily seen, even with the naked eye, a 
circular or slightly oval mark ; this is the line which indicates the boundary of 
the oral papilla (woodcut, fig. 2). On either side of it are two slits, about 0*5 
mm. in length, whose anterior extremities converge towards the middle line ; 
these are the orifices of depressions of the cuticle which contain the hooks, 
and the points of these may generally be seen, under a low magnifying power, 
protruding from them. 

The orifices of the sexual glands are somewhat difficult to observe, but in 
many cases they can be made out by careful examination, after the spirit has 
been allowed to evaporate from the specimens. The male genital openings are 
two in number, and are situated about 1 mm. behind the mouth, close to the 
middle line, and one at either side of it (PI. XXVII. fig. 1, g.o). The female 
genital apparatus opens also in the middle ventral line, but within less than 
1 mm. of the posterior extremity. All three are perfectly simple orifices, with- 
out any prominence. 

These were all the points worthy of note observed on the external surface. 
I could find no tactile papillae, such as are to be seen in Linguatida tcenioides, 
i although I looked for them with great care. 

The Body-Wall. 

The wall of the body consists of three distinctly marked layers — 

1. The Cuticle. 

2. The Epidermis. 

3. The Subepidermic Layer. 

1. The Cuticle (PL XXVII. fig. 9, cu) is a thin even layer which covers 
the whole surface of the body, including the invaginations in which the hooks 
are situated, and sends inwards prolongations which line the oesophagus, the 
rectum, and the genital ducts. Its thickness is on the average about 001 mm., 
and presents no noteworthy changes in different parts of the body, except that 
it is slightly thinner in the invaginated portions. 

There can be little doubt, from the analogy of different forms of life, that 
it is composed of chitin, although I attempted no investigation on this point, 
beyond ascertaining the fact that it did not dissolve in boiling solution of 
caustic potash. It is to all appearance quite structureless, even when 
examined under high powers of the microscope ; no trace could be found of 
the pores mentioned by Leuckart in L. tamioides* nor did the cuticle appear 
to be divided into two distinct layers, which was probably owing to the. 
immaturity of the specimens. 

* Bau u. Eutivick. d. Pentastomen, Leipzig u. Heidelberg, I860, p. 30. 



168 MR W. E. HOYLE ON 

The annuli, however, are perforated by large pores or " stigmata," arranged 
in from 6 to 8 irregular rows, but none of these are found in the interannular 
spaces. 

These stigmata are about 0014 mm. in diameter, and almost circular in 
form, and when seen en face present a double contour, which is due to the 
difference in density of the cuticle immediately surrounding the stigma ; when 
seen in section they appear very slightly constricted, so as to approach an 
hour-glass in shape (PL XXVII. figs. 9 and 11) ; the cuticle immediately sur- 
rounding the stigma is more highly refractile, and therefore probably also of 
greater density than the other portions ; but there is no clear line of demarca- 
tion between these as indicated by Leuckart in L. tcenioides* In some cases 
the portion of cuticle around the stigma is slightly thickened, although this is 
by no means constant. 

A surface view of the cuticle shows, moreover, a number of small irregularly 
oval markings, arranged in fairly even rings around the pores, and producing 
an appearance which recalls that of a transverse section of bone with its 
Haversian canals and lacunae (PL XXVII. fig. 2). These marks are due to 
the extremities of the epithelial cells, which form the next layer of the body- 
wall, as was very distinctly visible in one small portion of the cuticle which 
had this layer still attached to it. 

While treating of the cuticle it will be well to describe the hooks which are 
modified portions of it. Their form is shown in the drawing (PL XXVII. 
figs. 3 and 12) better than it can be described in words ; they are seen to be 
composed of two separate joints, moved by appropriate muscles, which will be 
treated of in the sequel. Their homology has been fully discussed by Leuckart 
in his classic monograph, and my investigations have not enabled me to add 
anything to what he has written upon this head. 

2. The Ejridermis, which follows immediately upon the cuticle, is a 
single layer of columnar epithelial cells, 012 to 02 mm. in thickness (PL 
XXVII. fig. 9, ep). The cells contain a distinct nucleus, generally oval in form, 
and situated in varying positions in different cells ; in some cases a nucleolus 
was visible. 

3. The Subepidermic Layer (PL XXVII. fig. 9, par) composes the greater 
part of the body-wall of the animal. It varies greatly in thickness, but on an 
average may be taken at 0*2 mm., the extremes being about 0*1 mm. and 035 
mm. ; as a general rule, it is thinnest along the dorsal surface, and in the 
narrow ventral intermuscular space (see p. 169) it is not unfrequently absent 
altogether. 

The cells of which it is made up are of very various sizes and shapes ; 
occasionally their diameter nearly equals the length of the epithelial cells, but 

* Loc. cit., p. 31, Tab. i. figs. 7 and 8. 



A NEW SPECIES OF PENTASTOMUM. 169 

in most cases they are only almost one-third the size of these. They contain a 
finely granular protoplasm, and a small spheroidal, ovoid, or somewhat irregu- 
larly shaped nucleus. They are packed closely together, and occupy the whole 
space between the subcuticular epithelium and the longitudinal muscle bundles. 

Among them are scattered the large glandular cells which will be described 
as part of the secretory apparatus (see p. 178) ; and they are traversed by many 
of the muscle-fibres, which will also be described in a special section of the 
paper. 

Towards the body cavity this layer, or the longitudinal muscle-bundles 
where they interpose, is marked off in the sections by a clear definite line, 
which becomes deeply stained. This I take to be the ccelomic epithelium 
(endothelium), but unfortunately none of my specimens were sufficiently well- 
preserved to enable me to speak with confidence on this point. 



The Muscular System. 

When the animal is opened by a median dorsal incision, and the body-wall 
spread out and examined from within, an appearance is seen such as is shown 
in PL XXVII. fig. 17. 

Longitudinal bands are crossed by transverse bands, and interspaces, 
roughly speaking, rectangular in form, are left between them. The ventral 
median line is marked by a series of square gaps, towards the margins of which 
are placed a number of radiating fibres. Along the lateral sides of the suc- 
cessive squares there stretch two broad bands (fig. 17, m.l', m.l'), which are com- 
posed of longitudinal muscular fibres, and, though somewhat variable in their 
breadth, are nearly as wide as the squares. Beyond these, again, are a number 
(commonly 8-10) of very much narrower longitudinal bands (fig. 17. m.l). 

A closer examination confirms the view that these longitudinal bands are 
composed of muscular fibres, but the case is otherwise with the transverse 
bands. These, as was pointed out by Leuckart, # are cellular in structure, 
and consist largely of the glandular cells which will be alluded to when treating 
of the subepidermic cell-layer (p. 178). They correspond with the external 
annulations of the animal, and on focussing deeply through these bands the 
stigmata are seen, whilst none are visible in the spaces between them. 

The muscular system of this parasite cannot, however, be fully understood 
by means of such a preparation as has just been described ; to render our 
knowledge complete, transverse sections are necessary ; and, when the informa- 
tion derived from these is taken into account, there are seen to be present 
three systems of muscular fibres — 

* Leuckart, he. cit, p. 39. 



170 MR W. E. HOYLE ON 

1. Transverse fibres, immediately underlying the epidermis. 

2. Longitudinal fibres, arranged in bundles, lying for the most part imme- 

diately below the coelomic epithelium. 

3. Oblique fibres, placed obliquely, however, both to the dorso-ventral 

plane of the body and to planes cutting it transversely. 

1. The Transverse Layer of muscular fibres is very thin, it being only one 
fibre thick ; in some cases there seemed to be two or even three such layers, 
but this appearance was probably owing to a slight obliquity of those particular 
sections. 

It is situated immediately within the epithelium, so that its fibres are for 
the most part parallel to- the cuticle, and they lie in planes which are approxi- 
mately transverse to the body of the animal. 

The appearance of this sheet of fibres is seen in PL XXVII. fig. 14 ; the 
fibres branch dichotomously, and at intervals unite with each other so as to 
form a fine network with elongated meshes, in which the cells of the parenchyma 
of the body- wall may be noticed. 

In the body proper of the animal this layer is developed almost exclusively 
on the sides, its fibres not often crossing the ventral, and hardly ever the dorsal 
median line. 

In one specimen about 1 mm. from the caudal extremity, I noticed a small 
patch of these fibres dorsally situated, but this might have been an individual 
peculiarity. The cephalic region, however, shows a great change in the 
arrangement of this layer, for there it is best developed on the dorsal and 
ventral aspects of the body, and to a much smaller extent on the sides. 

With respect to the nature of the individual fibres, but little can be said. 
They are very thin (about O'OOl mm.), and I could not detect in them that 
transverse striation which was noticed by Leuckart.* Some of the better 
preserved specimens showed, however, a kind of sarcolemma, an exceedingly 
thin sheath with a well-defined outline, and with small ovoid nuclei (PI. XXVII. 
fig. 16, nu). 

2. The Longitudinal Layer varies a good deal in its arrangement in different 
parts of the animal, and it will be advantageous to describe it as seen at about 
the middle of the body. A section taken in this situation is shown in PI. 
XXVII. figs. 10 and 13, m.l), and it will be at once noticed that the longitudinal 
muscles are situated at some distance from the external surface, being separated 
from it by the whole thickness of the body- wall. Its fibres, moreover, are 
grouped into definite bundles, which in the ventral region present a more or 
less elongated oval section, while in the lateral and dorsal regions they are 

* Loc. cit., p. 40. 



A NEW SPECIES OF PENTASTOMUM 171 

more nearly circular. A space free from muscles passes down the middle line 
ventrally, and this space, as we shall see, extends throughout the whole length 
of the animal. 

The bundles are thus arranged : — About four or five thin band-like portions 
are placed in the compartments formed by the splitting of the ventral margin 
of the oblique muscle-layer (fig. 10), and a somewhat thicker one lies on the 
inner surface of this layer close along its ventral margin. It is these bands 
which, overlapping each other by their outer margins, produce the appearance 
of a broad band, seen when the body-wall is examined from within (PI. XXVII. 
fig. 17, m.JI). 

Passing outwards there are next noticed smaller bands, of somewhat 
irregular figure in section, lying between the oblique muscles and the body- 
wall ; and then, after passing the point where the former of these are inserted 
into the latter, we come to a number (8-12) of rounded bundles which stand 
out from the body-wall, and would lie free in the body-cavity were they not 
covered with a thin membrane (ccelomic epithelium ?). 

In Leuckart's* description of these muscles in P. proboscAdeum, he 
mentions a space free from muscles extending down the dorsal median line of 
the animal similar to that above mentioned on the ventral aspect ; this state of 
things certainly did not obtain in the species at present under consideration, 
the longitudinal bundles succeeded each other quite regularly across the dorsal 
surface, and there was no thinning out of the mesoderm towards the median 
line (PL XXVII. fig. 10). Leuckart furthermore alludes to a division of each 
lateral muscle-mass into a dorsal and a ventral portion, but this also was not 
to be noticed in my specimens. 

Towards the tail (PI. XXVII. fig. 13) the muscular system gradually becomes 
less and less strongly developed, until at distances of less than 0*5 mm. clearly 
defined fibres are not to be found. The longitudinal and oblique systems 
appear to arise almost side by side, and the former is seen in sections a little 
less than 1 mm. from the hinder extremity to consist of about nine bundles on 
each side, which at this point show much less variety in size and shape than in 
other parts of the animal. Even here, however, there are a certain number of 
bundles, somewhat broader and more flattened, connected with the ventral 
margin of the oblique layer of fibres. The number of fibres in each bundle varies 
from about 10-30, but I could not make out satisfactorily any constant relation 
between the size of the bundles and their position. 

The fibres of which the longitudinal muscles are composed are almost 
0'008 mm. in diameter, usually oval in transverse section, except where they 
are rendered polygonal by mutual pressure. In most cases the inner portion 
of the fibre is pale in colour, and bordered by a fine deeply stained line 

* Loc. tit., p. 41. 



172 MR W. E. HOYLE ON 

(sarcolemma ?), in which is often seen an ovoid thickening which may be due 
to the presence of a nucleus. When they are well preserved these fibres show 
a clear transverse striation, the striae being separated from each other by a 
distance somewhat greater than the diameter of the fibre ; thus resembling 
those of the oblique fibres shown in PL XXVII. fig. 9. 

3. The Oblique System of muscles does not form a complete layer encircling 
the body, but consists of two muscular planes, which take origin near the 
ventral median line, and pass upwards and outwards, diverging at an angle of 
sixty degrees or more (PI. XXVII. fig. 10, m.o). Each plane appears in trans- 
verse section as a thin line, never thicker, and usually somewhat thinner, than 
a single fibre of the longitudinal muscles, but it shows a longitudinal striation 
as if composed of several fibrils. Near the ventral margin, and to some extent 
also near the dorsal, this lamella is seen to split into a varying number of 
thinner portions, between which are situated the longitudinal muscle-bundles 
as already described. 

This muscular group, however, is oblique in two senses ; as we have just 
seen, its fibres form two lamellae inclined towards the median plane of the 
body, but in addition to this, they pass obliquely downwards and forwards 
from one segment of the body into the next, as is shown in PI. XXVII. 
fig. 17. These fibres appear to be homologous with one half of the cruciform 
systems, which Leuckart describes and figures in P. proboscideum* but of the 
other half, those, namely, which proceed downwards and backwards, no trace 
was to be found. 

If it be correct to assume that the crucial fibres are the remains of one or 
two complete coats of oblique fibres, if Ave suppose the process of degradation 
carried still further, then the fibres passing downwards and backwards, not 
being of so great utility in the movement of creeping as those passing in the 
other direction, would be the first to disappear, and these latter only would 
remain. 

The fibrils of which this layer is composed are about 0*003 mm. in diameter, 
but they frequently exhibit a longitudinal striation, as though made up of still 
finer elements, and rarely the transverse striation was clearly exhibited 
(fig. 9, m.o). At intervals along the fibrils small darkly-stained nuclei are to be 
observed, but whether these belong to the sarcolemma or to the connective 
tissue, I was unable to discover. 

With respect to the mode of termination of the fibrils I can say but little ; 
it was often quite easy to follow them as far as the subcuticular epidermis, and 
in a few cases an appearance was presented such as is shown in PI. XXVI I. 
fig 16, giving decidedly the impression that they passed between the cells of 
this layer and are inserted directly into the cuticle. It would hardly be safe 



* 



Loc. cit, p. 41, Tab. i. fig. 10. 



A NEW SPECIES OF PENT ASTOM UM. 173 

to assert that this was generally the case, without an examination of fresh 
specimens, but it receives corroboration from Leuckart's account of P. probos- 
cideum. Some of these oblique fibres, on reaching the inner surface of this 
epithelium, turn and pass along it, thus assisting in the formation of the trans- 
verse muscular coat already described (fig. 16). 

Before quitting the muscular system, three points require a brief considera- 
tion, — the modifications which it undergoes in the tail and in the head, and 
its disposition with respect to the cephalic hooks. 

In the tail about the point at which the longitudinal fibres first became 
noticeable, the two lamellae have a somewhat different disposition ; instead of 
being inclined to each other at a considerable angle, they are much more nearly 
parallel, but separating from each other to give place to the intestine, they 
again approach slightly as they are inserted into the body-wall dorsally (PI. 
XXVII. fig. 13). 

The second point may be dismissed in a very few words ; on approaching 
the anterior extremity of the body, the splitting of the layer of oblique fibres 
towards its ventral margin is much further carried out (PI. XXVII. fig. 10, m.o), 
and the bundles of longitudinal muscle- fibres in relation with it are more nume- 
rous and larger, so that the ventral band of muscles is much more prominent. 
Concurrently with this change, but proceeding much more slowly, is a gradual 
diminution of the bundles of longitudinal fibres in the remaining portions of the 
body. As we reach points still more anterior in the animal (about on a level 
with the oesophagus) the ventral longitudinal bands undergo a similar diminu- 
tion, until in the neighbourhood of the hooks the regular longitudinal muscle- 
coat is represented only by a few isolated fibres. 

The oblique fibres, on the contrary, become more numerous, and are dis- 
posed more nearly parallel to the median plane of the body, until finally they 
come into relation with the hooks, and there become adapted to a special 
function, as will presently be seen. 

The Muscles of the Hooks. — The muscles which act upon the hooks have 
been studied by means of almost complete series of sections, both longitudinal 
and transverse, and though the general result of this inquiry is to corroborate 
Leuckart's # account of the matter, there are one or two differences which 
require to be noticed. 

Attached to the hook itself are four muscles, one to the dorsal and three 
to the ventral extremity of its base. 

The Extensor unci (PI. XXVII. fig. 12, u.e), as the first of the muscles 
above mentioned may conveniently be called, arises from the inner or ventral 
surface of the basal joint of the hook, and its fibres pass forwards and inwards, 

* Loc. tit., pp. 46, 47. 
VOL. XXXII. PART I. 2 F 



174 MR W. E. HOYLE ON 

to be inserted pinnately into a tendon which is attached to the dorsal angle of 
the hook. 

The Flexor unci (fig. 12, u.f) is inserted into the opposite angle of the hook, 
and arises, as Leuckart has well described, from the basal joint of the hook, its 
fibres crossing those of the muscle last mentioned. 

The Flexor accessories unci (fig. 12, u.f. a) is a long thin band which appears 
to arise in the mesoblastic tissue of the body, and passes forwards approaching 
the flexor unci on its ventral aspect at a slight angle, and is inserted close 
beside it. 

The Retractor unci (fig. 12, u.r) passes forwards and slightly towards the 
dorsal surface, and is inserted close to the two last. It acts to some extent as a 
flexor, but in conjunction with other muscles, more particularly the extensor, it 
produces that movement of retraction of the hook as a whole which Leuckart 
has described as occurring in the living Pentastomum, but which unfortunately 
I have not had the opportunity of witnessing. 

In addition to these four muscles are two attached to the extremity of the 
basal joint of the hook. 

The Protractor basis unci, arises from the anterior surface of the head, and 
passes backwards to be inserted into the posterior extremity of the basal joint 
of the hook. It consists generally of more than one slender bundle, and its 
action can be readily inferred from an inspection of the drawing (fig. 12, u.b.p). 

The Adductor basis unci (if it be allowed to use the word in the sense of 
drawing towards the ventral surface) is inserted along with the last named, but 
its fibres pass inwards from an origin near the ventral surface of the body 
cavity (fig. 12, u.b.a). 

In addition to the definite muscular bundles above described, a set of fibres 
arises from the cuticle all round the invagination in which the hook is situated; 
these muscles, which may be termed " retractors of the cuticle," are obviously 
charged with the function of facilitating the egress of the point of the hook 
from its sac and increasing the extent of its protrusion. 

The Digestive Tract. 

This portion of the animal's anatomy consists only of four well-defined 
portions — 

1. The Oral Papilla. 

2. The (Esophagus. 

3. The Stomach. 

4. The Rectum. 

1. The Oral Papilla. — In the description of the outside of the animal, men- 
tion has been made of a small circle lying between the two pairs of hooks. 



A NEW SPECIES OF PENTASTOMXJM. 175 

This is the external opening of an annular groove, whose depth is generally 
about equal to the diameter of the circle, though it is sometimes a little deeper. 
The two sides of the groove are almost in contact, so that its breadth is quite 
infinitesimal. 

From this it follows that the papilla, which is separated by the groove from 
the surrounding tissues, is a short cylinder, of about equal length and diameter. 
It is not quite regular in form, however, but the base is a little contracted from 
side to side, while the antero-external angle is sometimes a little rounded off 
(PI. XXVII. fig. 8). 

The cuticle which covers the free extremity of the papilla is not to be dis- 
tinguished from that covering the remainder of the body, while that upon the 
sides of the groove is a little thicker, and absorbs the staining material (heemat- 
oxylin) more greedily, and is provided with a number of small spines (fig. 4). 

The subcuticular epithelium of this organ presents no note worthy of modifi- 
cations, but its muscles are rather complex, and indicate that it is an organ of 
considerable functional activity. 

The papilla itself contains two (possibly three) sets of muscular fibres — the 
first traverses it almost parallel to the longitudinal axis of the body, slightly 
approaching the ventral surface as it passes backwards (PI. XXVII. fig. 8) ; 
the second passes from its base towards the free extremity, bending slightly 
inwards as it proceeds. Some of the sections of the papilla seemed to show 
a thin marginal layer of fibres, divided transversely, which would of course 
constitute a sphincter, but these appearances were so uncertain, that I do not 
feel justified in doing more than merely alluding to them. 

In addition to these, a clearly-defined retractor bundle runs obliquely for- 
wards from the middle of the body into the papilla (PL XXVII. fig. 8), while 
all around it slender groups of fibres pass outwards, and are inserted into the 
cuticle. 

From a consideration of the structures above described, it seems probable that 
this papilla can be protruded after the manner of a proboscis ; the last named 
muscles being specially efficacious in assisting this action ; the subsequent retrac- 
tion also is amply provided for. Furthermore, the intra-papillary antero-posterio 
fibres will, by their contraction, increase the space behind the papilla, which 
the retraction and consequent swelling of this latter will again diminish, thus 
obviously aiding the operation of deglutition. A third function possible to this 
organ is that of a sucker, to secure the adhesion of the parasite to its host. 

No structure of this kind would appear to exist in L. tamioides, whose 
mouth is merely " a widely gaping orifice " (eine grosse und klaffende 
Oeffnung), # followed by a funnel-shaped pharynx, along which the chitinous 
lining is continued as far as the stomach itself. 

* Leuckart, loc. cit. p. 55. 



176 MR W. E. HOYLE ON 

2. The (Esophagus commences at the bottom of the groove posteriorly, and 
after a variously curved course, opens into the ventral surface of the stomach 
some distance behind its anterior extremity (PI. XXVII. fig. 8, oe). Its course 
is at first obliquely upwards and backwards, and its transverse section is cres- 
centic, the horns being directed ventrally (fig. 6, r) ; the dimensions of this 
crescent are 016 mm. across the horns, while the lumen of the passage is only 
0012 mm. in width. This portion of the oesophagus is lined with chitin pro- 
longed from the external covering of the body ; and its wall is composed of a 
mass of cells in which distinct muscular elements could not be made out. 

The oesophagus then turns directly backwards to pass beneath the anterior 
nerve commissure (fig. 8, a.n.c), and at this point its structure undergoes a 
change ; the cuticular lining after becoming gradually thinner, entirely dis- 
appears, and outside the cellular wall there lies a covering of muscular fibres 
arranged as a sphincter ; while, in addition to all this, the section of the tube 
becomes irregularly elliptical instead of crescentic, the transverse and dorso- 
ventral diameters being 0*1 mm. and 0'012 mm. respectively. 

When the oesophagus has passed through the nerve collar, its direction 
tends more upwards, and very slightly forwards, and its lumen assumes an 
irregularly stellate form, owing, probably, to the contraction of the sphincter 
muscles, and consequent puckering of the cellular lining (fig. 6, /). It now 
turns backwards, and at the same time comes to lie in a mass of cells situated 
immediately below the intestine. The elements composing this mass are for 
the most part of ovoid form, the greatest diameter averaging 0016 mm. ; they 
have a finely granular content, and a large deeply-stained spheroidal nucleus, 
with a nucleolus. Their function must remain to a large extent the subject of 
conjecture ; their histological characters and situation would suggest that they 
form a gland, but none of the sections examined have revealed any trace of 
duct or of excretory openings in the oesophageal wall. 

After a short course through this gland-like organ, it turns directly upwards, 
and opens upon a small elevation in the floor of the intestine, at a point about 
1 mm. behind its anterior extremity (PI. XXVII. fig. 8). 

3. The Stomach (Chylusmagen of Leuckart) needs only a few words of 
description. As stated above, it presents anteriorly a rounded coecal extremity 
about 0*5 mm, in length, behind which is the opening of the oesophagus (PI. 
XXVII. fig. 8). Its form is, speaking roughly, cylindrical, slightly tapering, 
however, as it passes backwards, and it lies evenly in the middle of the body 
cavity ; its greatest diameter being about 075 mm. A little less than 1 mm. 
from the posterior extremity of the body the stomach terminates by opening 
into the rectum. 

Of all the organs of the body the digestive tract was, unfortunately, the 
worst preserved, so that I am unable to give information of any great value as 



A NEW SPECIES OF PENTASTOMUM. 177 

to its histology. It is lined by a single layer of nucleated epithelial cells, and 
the remainder of the wall is made up of two indistinctly cellular layers, in 
which I failed to distinguish any definite muscular elements (figs. 5 and 10). 

The wall thus composed is about 042 mm. in thickness near the head, but 
it commonly increases to about double this, and is much more compactly con- 
stituted in the more posterior portions of the body. 

Two mesenteries (fig. 5) support this portion of the alimentary canal ; these 
are not diametrically opposite to each other, but are separated by an angle of 
90° to 120°. They are thin lamellae (0*021 mm. thick), made up either of small 
rounded cells, or else of fibres placed longitudinally ; on an average, two of 
these make up the thickness of the lamina. The mesenteries commence as 
continuous membranes about one and a half millimetres from the hinder 
extremity of the body, although traces of them are visible in transverse sections 
posteriorly to this. 

In addition to the stomach, they support the hook-glands (PI. XXVII. fig. 
10), and in the anterior portion of the body the vasa defer entia come into rela- 
tion with them, as will be more fully explained when speaking of those organs. 

There would appear to be in L. tamiaides nothing homologous to the struc- 
ture just described, unless it is to be found in a number of distinctly muscular 
fibres which arise from the stomach, and spreading out in the form of a fan, 
unite with the muscular wall of the body ; * but the differences between these 
two sets of structures are so many, that it would scarcely be justifiable to 
regard them as homologous, save as the result of an embryological inquiry. 

4. The Rectum (PL XXVII. fig. 7) is about 075 mm. in length ; in section 
it is compressed dorso-ventrally, its transverse diameter being 017 mm., while 
its upper and lower surfaces are almost in contact ; it is lined with cuticle, 
0*015 mm. in thickness, prolonged from the external surface of the body, below 
which is a layer of cells, forming part of the chitinogenous layer. Muscular 
elements seem to be entirely absent. 

Secretory Organs. 

Three distinct sets of organs must, in the present state of our knowledge, 
be grouped together under this head, although they differ widely in structure 
and probably in function also. 

They are — 

1. The Hook-Glands. 

2. The Parietal Cells. 

3. The Stigmatic Cells. 

1. The Hook-glands (Hakendrusen, Leuckart) are undoubtedly the same 

* Loc. cit., p. 59. 



178 MR W. E. HOYLE ON 

structures as van Beneden described in his P. Diesint, V' arid" as those to which 
Leuckakt alludes in P. cyli/ulricum, P. oxycephalum, &c.f They are elongated 
bolster-shaped bodies, tapering slightly towards either end and flattened on the 
median surface which is in relation with the intestine (PI. XXVII. fig. 10, h.g). 
They extend forwards into the head, but about the point where the oesophagus 
opens into it they leave the intestine, and passing outwards unite with the 
body-wall ; posteriorly they extend to within a few millimetres of the hinder 
extremity of the body. 

Their length is thus very little less than that of the entire animal, while 
their average diameter is about - 7 mm., so that they fill up the greater part of 
the body-cavity on either side of the intestine. 

Each gland is covered by a delicate membrane, and within is made up of 
very large cells varying 0'07 mm. to 01 5 mm. in diameter, of very diversified 
shapes and packed closely together. 

The cells were found to contain a coarsely granular protoplasm, and a 
large nucleus (0*02 mm. in diameter) in which a nucleolus could only very rarely 
be distinguished. 

In the centre of the gland may be seen the duct (fig. 10, h.g'), a tube 0*02 mm. 
in diameter, with a lumen of O'OOS mm., lined with a very delicate layer of 
chitin. This duct was traced forwards through a series of transverse sections 
nearly as far as the bases of the hooks ; beyond this point, however, it could not 
be followed ; but there can be no reasonable doubt that it opens in the invagina- 
tion of the cuticle in which the hook is situated, as described by Leuckart. I 
could detect no ducts passing towards the mouth, but only the two pairs pro- 
ceeding in the direction of the hooks ; neither the duct nor any portion of the 
gland passes through the nerve ring, as in P. oxyce$)haliim.\ 

These glands would seem from their position and relations to be homologous 
with the salivary glands of other Arthropoda ; the fact of their opening at the 
base of the appendages and not into the cavity of the mouth might be an 
obstacle to the adoption of this view, unless perhaps these are to be regarded 
as homologous with the jaws rather than with the limbs of allied forms. 

2. The Parietal Cells (PI, XXVII. fig. 9, p.n) I propose for the present to 
term a number of large oval cells scattered in the mesoderm of the body-wall, 
because at present no opinion can be offered as to their function. They consti- 
tute one of the most conspicuous characters seen in the examination of sections, 
both longitudinal and transverse. 

In form they are ovoid, generally flattened by mutual contact, and averaging 
03 mm. in diameter ; they contain a deeply stained spheroidal nucleus of 

* Ann. d. Sci. Nat., ser. 3, t. xi. p. 324, 1849. 
f Letjokart, he. cit., p. 67. 
\ hoc. cit., p. 67. 



A NEW SPECIES OF PENTASTOMUM. 179 

about 0'008 mm. in diameter, within which a small nucleolus is generally to be 
seen ; the protoplasm is finely granular and faintly stained. 

These cells are arranged in groups of 2-5, and very commonly at the point 
where several cells meet may be observed an oval speck, from which fine radi- 
ating lines branch out (figs. 9 and 15). The similarity between this appearance 
and that depicted in some of Leuckart's figures will be at once apparent.*" 

The distribution of these cell-groups next demands attention ; they lie 
among the smaller mesodermic cells constituting the body-wall, about 
midway between its inner and outer surfaces, and are disposed in zones, corre- 
sponding with the annuli of the body, and consequently with the stigmata, none 
being found in the interannular spaces. It is, in fact, the presence of these cells 
which causes the swelling of the annular regions of the body and the greater 
stiffness of the wall in those parts, which has been already alluded to. 

In the annuli, however, these cell-groups are very closely placed, and in a 
transverse section they seem to form an almost continuous zone ; more than 
fifty can often be seen in a single circumference. 

The homology of these cells next demands our attention. Their position 
would seem to show that they correspond to those cells of L. toenioides which 
Leuckart has called the hook-gland (Hakendrlisen, see Tab. i. fig. 11 of his 
monograph), and this view is strikingly confirmed by a study of their appear- 
ance (a/, fig. 15 with Tab. i. fig. 17). The form of the cells is the same, as also 
their arrangement in acini composed of 2-5 ; the radiating apparatus also, 
which Leuckart regards as the commencement of the excretory apparatus, is 
the same in both. But if we admit this hypothesis we are placed on the horns 
of a dilemma, for we have in the creature before us a structure which is homo- 
logous with the hook-gland of L. toenioides, and another organ which is beyond 
all question the homologue of a gland which Leuckart finds in P. proboscAdeum 
and other species, and which van Beneden has described in his L. Diesingii, 
and which, again, is declared to be the homologue of the hook-gland of L. 
tamioides.f Thus we have two separate organs both corresponding to the same 
organ. It appears to me that at present the only course open to us is to assume 
that we have here a condition in which there is a double set of organs, one of 
which is lost in certain forms, while the other disappears in others. This does 
not seem satisfactory, however, because both structures appear to be very Avell 
developed, and have by no means the aspect of rudimentary structures. 

In the face of this difficulty, I regret the more that I was unable to trace the 
course of the excretory apparatus of these peripheral gland cells, even after the 
most careful scrutiny of the sections. This knowledge might have solved the 
mystery, but at present it must be left until some future occasion may furnish 
a supply of better preserved material. 

* Loc. at., Tab. i. fig. 17. f Loc. cit,, p. 67. 



180 MR W. E. HOYLE ON 

With regard to the function of this cell-system, I have, as will be inferred 
from what has just been stated, no theory to offer; if it be really a portion of 
the hook-gland, then the suggestions of Leuckart seem the most apt that can 
be offered, and if not, the discovery of the destination of the secretion must 
precede any further hypothesis. 

3. The Stigmatic Cell-groups (P1."XXVII. figs. 9 and 11, s.c) have been 
already alluded to as situated immediately within the stigmata. They are 
spheroidal in form, and their inner surface projects only a little beyond that of 
the subcuticular epithelium, so that they have an average diameter of about 
02 mm. They are not very transparent, and take up the straining material 
eagerly, so that their structure is somewhat difficult to make out. Each con- 
sists of from six to nine small cells, with clear or clouded protoplasmic contents, 
and a comparatively large variously-shaped nucleus. The outer aspect is 
moulded into a kind of short neck which lies within the stigma, and is closed 
by a fine very darkly stained line. 

Such being the appearance of these structures, it becomes necessary to 
inquire into their homology and function. In Leuckart's classic # work there 
are described in the earlier developmental stages of L. twnioides vesicles of 
clear fluid in relation with the stigmata, and these in the adult are replaced by 
large cellular processes which project into the body-cavity. It would seem, 
then, that we have in the subject of the present investigation a condition inter- 
mediate between the two just described, and this is rendered more probable 
inasmuch as Leuckart speaks of and figures an incipient segmentation. 

These cell-groups are possibly homologous with the subcuticular glands 
described by Kolliker in certain insects ;t it is scai'cely possible that they have 
any relation other than a merely analogical one with glands, which they closely 
resemble in structure, described by Andreae in Sipunculus nudus.% 

With respect to the function discharged by these structures it seems quite 
possible that they take part in the formation of the cyst which encloses the 
animals, unless they be excretory in nature, and destined only to come into 
full activity on the further development of the animal ; it is not impossible, 
however, that both these suggestions may be true. 

The Nervous System. 

As might have been anticipated, the nervous system of the subject of this 
paper shows but slight differences from that of any similar forms which have 
hitherto been examined. It consists of a single median ganglion, showing, 
however, traces of a primitive division into two lateral halves, and of about 

* Loe. cit., p. 33. 

t Verhandl. d. phys. med. Vero'ns Wiirzlmrg, p. 76, 1857. 

% Z itschr.f. iviss. Zool., Bd. xxxvi. p. 201, Taf. xii., figs. 1 and 4, 1881. 



A NEW SPECIES OF PENTASTOMUM. 181 

equal length and breadth (0*28 mm.), while its thickness amounts to about 
014 mm. A general view of its form and position, with the branches given 
out from it, is given in the dissection depicted in PI. XXVIII. fig. 16, n.g. 
The two larger branches, which pass backwards, can be traced for more than 
half the length of the animal ; they lie in the main parallel to each other, one 
on either side of the ventral median line. From either side of the large ganglion 
a branch passes along the oesophagus, and probably reaches the oral papilla. 

In connection with the structure described by Lienard * in several other 
Arthropods (Spirocyclistus, Cossus), it is interesting to note that the praeoeso- 
phageal commissure in my specimens was double, and from the anterior cord 
two branches proceeded forwards. 

The minute structure of the nervous system was so ill-preserved that no 
observations of value could be made upon it. 

The Generative Organs. 

Both male and female specimens were fortunately present among those I 
had for examination, but while the genital apparatus of the former presented 
some noteworthy arrangements, that of the latter was not specially remarkable. 

The Male Organs. 
These may conveniently be described under the following heads : — 

1. The Testis. 

2. The Vesicula seminalis. 

3. The Vas deferens. 

4. The Cirrus Sac. 

1. The Testis (PI. XXVII. fig. 5 ; PI. XXVIII. figs. 1-6, /) is situated on the 
dorsal surface of the intestine ; it is an unpaired, long, very thin walled sac, 
extending from a point some 4-5 mm. behind the head, to within about 1 mm. 
of the posterior extremity, where it ends in a mass of small parenchymatous 
cells, which lie on the dorsal aspect of the intestine. Its greatest breadth 
(measured from side to side) is 0*7 mm., whilst its thickness (dorso-ventral) 
will be rather more than one-third of this. 

The wall of this gland consists of a thin, and to all appearance, structureless 
membrane, which becomes very deeply stained by hematoxylin, and measures 
0004 mm. in thickness. It is attached to the dorsal wall of the body-cavity 
by a thin cellular mesentery (PI. XXVIII. fig. 3, m.e) which is precisely similar 
in structure to those supporting the intestine, already described. 

In the immature specimens under consideration, the gland contained only 

* Lienard, "Constitution de l'anneau cesophagien," Arclriv. d. Biol.,%. i. p. 381, 1880. 
VOL. XXXII. PART J. 2 G 



182 MR VV. E. HOYLE ON 

a few masses of protoplasm of very variable size and shape, each usually 
possessing several nuclei, but not divided into distinct cells (fig. 2) ; they clearly 
represent the earlier stages in the development of the spermatozoa as figured by 
Leuckart."* Anteriorly, as well as posteriorly, the testis becomes narrower 
though not to the same extent, and its inferior wall becomes thickened by a 
deposition of small cells on its outer surface. Farther forward two grooves 
appear in this mass of cells, which gradually become deeper until eventually 
they become roofed in, and thus converted into two tubes (figs. 4 and 5). 
The tissue in which these tubes lie is composed of small rounded cells, which 
vary from 0*004 mm. to O'OOS mm. in diameter, and are provided with small 
spheroidal nuclei. In the tubes they seem to form a single layer of columnar 
epithelium, but this was so badly preserved that I can give no further 
particulars concerning it. 

The lumen of these tubes gradually becomes regularly oval and very much 
smaller, being in some sections barely perceptible, and in certain cases the cells 
seem to have a tendency to segregate into a separate covering for each tube, 
as indicated by a splitting in the cell mass ; these fissures do not, however, 
extend far, and may be due only to the shrinking of the tissue in hardening 
(fig. 6). 

On examination of PL XXVIII. figs. 4-6, it will be noticed that the cavity 
of the testis extends forwards some distance over this tube, but it becomes 
gradually smaller and eventually terminates blindly. 

These two tubes continue separate although enclosed within a common 
investment for a distance of 0*2 mm., and then fuse into a thinner walled 
cavity, roughly oblong in section, and supported by a continuation of the same 
mesentery as the testis. At this point we may consider the second part of the 
genital tract to begin. 

The two tubes are, of course, indications of the primitive symmetry of the 
sexual organs, and it may be worth while to mention that in L. tcenioides the 
testis is double (though both glands eventually open into an unpaired tube), 
while in P. oxycephalum and P. proboscideum only a single gland is present. 

2. The Vesicula seminalis (PI. XXVIII. fig. 1, v.s), (Samenblase, Leuckart). 
I apply this name to the structures now to be described, because they seem 
to correspond to a tube, bifurcated at its extremity in L. tcenioides, and near 
its commencement in P. proboscideum. In the present instance the lumina of 
the two tubes become united, and also first enlarged, for as may be seen by 
comparing figs. 6 and 7, the cavity of the single vessel is much greater than 
those of its two components. The wall is made up of cells of precisely the 
same character, but is only about 024 mm. in thickness on the average. 
The layer of columnar epithelium is distinct in its interior. 

* Log. eft., Tab. ii. fig. 14. 



A NEW SPECIES OF PENTASTOMUM. 183 

After a course of about 001 mm. this vesicula seminalis becomes divided 
into two by a septum which rises from its ventral surface (fig. 7), and very 
shortly it divides into two quite distinct tubes (figs. 8 and 9). This junction 
between the two vesiculse seminales is of considerable morphological interest, 
because it is the first trace of a condition which is carried further in P. pro- 
boscideum, and reaches its fullest expression in the large median sac found in 
L. tcenioides (cf. Leuckart, loc. tit, Tab. ii. figs. 9 and 10). 

At this point the dorsal mesentery splits, and a portion accompanies each 
tube. 

The two branches of the vesicula seminalis now diverge from each other, 
and passing round the intestine, become united with the copulatory apparatus 
which lies upon its ventral surface ; as they separate they first of all lose their 
mesenteric connection with the dorsal body- wall, although the rudiment of the 
mesentery is still to be seen after they have become detached from it. In their 
further course they approach the hook-glands, which they gradually traverse, 
passing through the middle of the gland and not between it and the intestine. 

The rudimentary mesentery now demands a moment's notice ; it passes 
forwards, becoming slightly wider, and just at the point where the vesicula 
seminalis emerges from the hook-gland, it becomes connected with this latter ; 
so that now each hook-gland is supported by two mesenteries, one which it has 
had throughout the whole length of the body, and another which it has derived 
from the genital organs. 

In this connection it may be well to say a word or two with respect to the 
size and structure of the vesicula seminalis. It is about 2 mm. long, and 
of a regular oval section, its greater and lesser diameters being 0*178 mm., 
and 0*1 mm. respectively, being slightly larger about the middle of its length. 
Its wall is made up of two layers of about equal thickness (0*02 mm.); the 
outer of which consists of a mass of cells very similar to those mentioned at 
its commencement, but rather more irregular in outline, and varying consider- 
ably in size, and provided with distinct ovoid nuclei. The inner coat consists 
of a single layer of elongated columnar epithelial cells, also nucleated and 
separated from each other by an undulating boundary line. 

The vesicula seminalis now lies free in the body-cavity for a short distance, 
and then becomes attached to the vas deferens,, which will be presently 
described. 

At this point one of the most remarkable peculiarities in the organisation of 
the animal comes into notice. The lumen of the vesicula seminalis becomes 
excluded, and is not continuous with that of the vas deferens. 

This last is a tube regularly elliptical in section, of sharply-defined even 
contour and compact walls ; applied to the dorsal wall of this is a mass, oval in 
section, of much looser tissue, which is in fact the wall of the vesicula seminalis, 



184 MR W. E. HOYLE ON 

but there is no intimate union between the two, which are separated by a clear 
line of demarcation. 

The truth of this observation, so exactly opposed to what might have been 
expected, has been confirmed by the preparation of a very careful series of 
transverse sections, which show the one tube lined with a perfectly smooth 
layer of epithelium, passing by the other, utterly ignoring, if the expression may 
be allowed, its proximity, while the vesicula seminalis fades away in a mass of 
rather loose cells without showing the least desire to unite with its companion. 

PI. XXVIII. fig. 15, shows the last section which contains a trace of the 
vesicula seminalis, in the one next behind the lumen, though small, was quite 
apparent, and in the next anterior there is no trace of it whatsoever. 

Observations suggested by this arrangement will be deferred until the next 
portion of the generative system has been described. 

3. The Vas deferens (Pl.-XXVIII. figs. 1, 10, and 12, v.d) is a short tube which 
passes' forwards from the termination of the vesicula seminalis and opens into 
the cirrus sac ; this portion of it is about 15 to 2 mm. in length, but it is pro- 
longed backwards into accecal process (blindschlauchartiger Anhang, Leuckart) 
whose length commonly exceeds that of the anterior portion by two to three 
times ; it is variously curved, and in caie case was observed to open again into 
itself, and thus to form a complete tubular ring. 

The structure of this vessel is the same throughout, its average diameter is 
about 6"08 mm., that of its lumen 0*024 mm.; within it is lined by a thin layer 
of chitin derived from the external covering of the body, externally to which is 
seen a compact mass of nucleated cells radially disposed and to all appearance 
epithelial in nature. I was unable to discover with certainty the presence of 
muscular elements in this wall, although Leuckart observed them in L. tamioides, 
and based upon that fact the hypothesis that the ccecal prolongation is an organ 
for the propulsion of the semen. # For the greater part of its length it possesses 
a further adventitious covering of tissue similar to that in which the vesicula 
seminalis terminates. 

The opening of this organ into the cirrus sac will be described under that 
heading (p. 185). 

The want of continuity between the vesicula seminalis and the vas deferens 
becomes comprehensible wjien we consider what is known of the developmental 
history of this group of animals, for it would appear from the researches of 
Leuckart that one portion of the generative apparatus takes origin by the 
segregation of cells within the body, while another portion is formed by 
invagination of the external surface. When it is remembered that the vas 
deferens is connected with the external surface, and bears further marks of its 
origin in its chitinous lining, and that the vesicula seminalis presents a marked 

* Loc. cit., p. 75. 



A NEW SPECIES OF PENTASTOMUM. 185 

contrast in appearance, and has no such lining, it would seem justifiable to 
assume that the point where these two come into relation with each other is 
also the point where what may be termed the inward and outward growing 
portions of the generative apparatus meet, Furthermore, the immaturity of 
the specimens before us, indicated by their encysted condition, is in support of 
this, for it is quite conceivable that, as sexual maturity approaches, a connec- 
tion might be formed between these two canals. It is to be noted, however, 
that in Leuckart's figures of the sexual organs of L. tamioides, the channel is 
shown as quite pervious from the exterior to the testis even in so early a stage 
as that known as P. denticulatum* which measures only 4'5-5 mm. in length ; 
but in describing the stage immediately preceding, which has a length of 
3 mm., he mentions that the communication with the cirrus sac and the hinder 
portion was not clearly observed (" Eine Communication mit den dahinter 
gelegenenen Leitungsapparaten wurde mit Bestimmtheit nicht beobachtet").t 
If this explanation be the correct one, it is curious that the species before us 
should present such a striking embryonic feature when the remainder of its 
organisation has attained such a comparatively advanced stage of development. 

4. The Cirrus Sac is shown in longitudinal section in PL XXVIII. fig. 10, 
and may be seen to be roughly divisible into two portions, — a solid part through 
which the vas deferens passes, situated on the dorso-lateral aspect, and a 
hollow part placed nearer to the ventral line. The latter portion is, speaking 
roughly, ovoid in form and slightly flattened in the radial direction of the 
animal's body, as seen in the section (fig. 11): anteriorly it gives off a tube 
from either side (fig. 10). One of these is the ejaculatory duct, the position of 
whose aperture near the middle line of the body has been already described ; 
its lumen becomes gradually smaller until it reaches 0005 mm. 

The other tube-duct of what seems to be a gland, which, under the name of 
accessory, will be presently described. 

The wall of this saccular portion is on the average about 0*036 mm. in 
thickness ; its innermost layer is of chitin so thin that it appears only as a fine 
though very distinct line under a power of 400 diameters ; next follows an 
epithelial layer, 0-008 mm. in thickness, of nucleated columnar cells; the 
remainder of the wall being composed of small cells among which run a number 
of muscular fibres, these last being confined to the anterior portion of it. 

The solid portion of the cirrus sac is an ovoid mass somewhat smaller than 
the other part, the wall of which covers it to a certain extent, though even- 
tually it fuses with it. Through the middle of this mass of cells passes the canal 
of the vas deferens, slightly widening as it approaches the sac until it ends in a 
short groove (PI. XXVIII. fig. 10 ; also in section fig. 11, v.d). 

A short distance posterior to this is another orifice leading into a cavity 

* Loc. cit., Tab. iv. fig. 11. f Loc. cit., p. 134. 



186 MR W. E. HOYLE ON 

which contains the " Chitinzapfen " of Leuckart (fig. 10, c.z). This is a 
cylindrical body, pointed at its free extremity, and for the greater part of its 
length attached by one side to the interior of the cavity in which it lies 
(fig. 12, c.z) ; this cavity is only just large enough to contain the organ, whence 
in section its lumen appears as a slit almost annular in form. Between this 
part of the cell-mass and that which contains the vas deferens there is very 
often a fenestra, as in the case shown in the drawing. 

With respect to the structure of this portion of the cirrus sac, it consists in 
the main of small (0-002-0-005 mm.) nucleated cells, closely packed. In the 
" Chitinzapfen " these show a tendency to a radial arrangement, and often leave 
in the centre an irregular gap, which does not seem, however, to be of any 
morphological signification. 

The epithelial lining of the vas deferens here assumes a most distinctly 
radial arrangement (fig. 12, v.d), the cells being very long and slender, and 
with nuclei either at one extremity or the other, rarely in the middle ; exter- 
nally to this is a thinner layer of cells, which is an extension of the common 
wall of the cirrus-sac. 

Of the cirrus itself I could find no trace whatsoever, and am consequently 
led to imagine that it has not yet made its appearance ; if this be so, we have 
here another point in which this animal corresponds with a very early stage of 
L. tcenioides. It is possible, however, that in this species no cirrus is ever 
formed, and that the " Chitinzapfen " does duty as a copulatory organ ; in any 
case, I should be disposed to regard this as a kind of dilator for opening up the 
sexual canal, either for the immediate flow of the semen, or as a preparation 
for the passage of the slender cirrus, which by itself would hardly seem to be 
fitted for such a purpose. In this process a very important service would be 
rendered by the muscles which pass transversely across the sides of the cirrus 
sac, for they would approximate the " Chitinzapfen " to the sexual orifice. 

The Accessory Gland (PI. XXVIII. fig. 13), above alluded to, is a flattened 
mass of cells lying beside the intestine about the spot where the oesophagus 
enters it, and stretching in a dorsal direction as far as the hook-gland. The 
duct passes upwards and forwards through the middle of it, and is surrounded 
by a space, crossed by numerous fine threads which are probably minute rami- 
fications of the duct, although it could not be made out witli certainty that they 
were hollow. At the extremities of these are groups of cells (0*008-0-014 mm. 
in diameter), rendered polyhedral by mutual pressure, and provided with 
relatively large nuclei, in some of the larger cells 0'008 mm. in diameter. 

As to the secretion of this gland and its function, I have been able to make 
no observations. 



A NEW SPECIES OF PENTASTOMUM, 187 

The Female Organs. 
But little is to be said on this subject, because these organs were in a very 
unsatisfactory state of preservation. They consist of — 

1. The Ovary. 

2. The Oviducts. 

3. The Keceptacula Seminis. 

4. The Vagina. 

1. The Ovary (PI. XXVIII. fig. 18) occupies a position exactly corresponding 
to that of the testis, but is very much smaller. It is in fact at this stage of the 
animal's growth merely a narrow tube, about 0*015 mm. in diameter, passing 
with a sinuous course down the median dorsal line. It is attached by a 
mesentery similar in structure to, but much thicker than, those which support 
the testis and intestine (PL XXVIII. figs. 3, 14, &c). 

It consists of a thin layer of small nucleated cells, and has a considerable 
lumen ; but I was unable to make out anything regarding the development of 
the ova. 

2. The Oviducts are two in number, and like the vasa deferentia, pass round 
the intestine, and eventually meet in the middle line below it (PL XXVIII. 
fig. 16, o.d), where they open into the vagina. 

In structure they seem to resemble the ovary itself. 

3. The Receptacula Seminis (PL XXVIII. fig. 16, r.s) are two flattened 
oval sacs, nearly 1 mm. in length, and situated one on either side of the middle 
line immediately posterior to the oviducts. Anteriorly, and towards the 
median line, the cavity of the sac enlarges, and into this dilated portion projects 
a papilla on which opens, by a stellate orifice, the tube by which the sac com- 
municates with the vagina. 

The cuticular lining of the vagina could be followed to this orifice, but I 
could find no trace of it on the interior of the sac ; the wall of which consists 
of a very compact mass of minute nucleated cells ; it is about 025 mm. thick 
on the average, and is lined with what appear to be the remains of an epithelial 
layer. 

4. The Vagina (PL XXVIII. fig. 16, v) is simply a narrow tube, which 
passes directly backwards from the point of union of the oviducts to open in 
the ventral line within a millimetre of the anus. Typically it lies in the ventral 
median line, but in one specimen of which I made sections, it lay at one side, 
between the hook-gland and the muscles of the body- wall. 

It has a lumen of about 0*008 mm., and is lined by a delicate layer of 
cuticle, immediately external to which is found as usual a layer of columnar 
epithelial cells. These again are surrounded by another layer, made up of 



188 MR W. E. HOYLE ON 

rounded nucleated cells about two deep, and having a diameter of some 
0-007 mm. 

Systematic Position. 

The parasite which has just been described finds its nearest congener in 
Pentastomum polyzonum, Harley."" It is distinguished from it, however, by 
the number of segments, which in the females under consideration amounts to 
18-22, whilst in the adult females of P. polyzonum hitherto described t it does 
not exceed 19, and it is very unlikely that an immature form should have more, 
though it would very probably have fewer segments than the adult. In this 
case the difference in size is of course valueless as a specific character. 

I propose therefore to make the specimens above described the type of a 
new species, whose diagnosis would be provisionally as follows : — 

Pentastomum protelis, n. sp. 

Body cylindrical in the anterior half, slightly tapering posteriorly, terminal 
segment obtusely pointed. No clear distinction between cephalolhorax and 
abdomen. Head hemispheroidal, equal in diameter to the body. Mouth fur- 
nished ivith a papilla, perhaps a protrusible proboscis. No accessory hooks. 
Stigmata arranged in numerous irregular roivs on all the segments. Male, 
13-17 mm. in length, with 16 or 17 annuli. Female, 20-25 mm. in length, with 
18-22 annuli. Habitat, the mesentery of Proteles cristatus, enclosed in a con- 
nective tissue cyst. 

It is, of course, possible that some future investigator will demonstrate the 
identity of this form with an early stage of P. polyzonum, and this possibility 
is increased by the fact that specimens of this species were found in an 
African serpent,^ of which part of the globe Proteles cristatus is also an 
inhabitant. 

If such should be the case, Leuckakt's opinion that P. Diesingii, v. Ben., is 
the immature forni of this would be untenable, for this form exhibits distinc- 
tions in its body form, oral papilla, and muscular system, sufficient to prove 
its specific distinctness from the subject of this paper. 

I propose now to make a few concluding observations on the subdivision of 
the family Pentastomidre. 

In the brief systematic portion of Leuckakt's § work, the species are grouped 
under two headings, which are regarded as being of sub-generic value — 

* Proe. Zool. Soc. Lond., part 25, p. 115, 1857. 

t B' ' i.. Ann. <nt<l Mag. Nat. Hist., ser. 5, vol. vi p. 176, 1880. 

X BbMi Im eit. p. 173. § Luc. eit, p. 152. 



A NEW SPECIES OF PENTASTOMUM. 189 

Linguatula, "Corpus depressum." " Cavitas corporis in latera annulorum 
porrecta, pectinata." 

Pentastomum, "Corpus teretiusculum. Cavitas corporis continua." 

It appears to me, however, that we see now sufficient anatomical distinc- 
tions in the works of previous authors,* and in the research which has just been 
recorded, to justify the elevation of these two groups to the position of distinct 
genera. 

In the first group, for example, the hook-gland is diffuse, the oesophagus 
opens into the anterior termination of the intestine, the testis is double, and the 
vesicula seminalis single, while in the second group the hook-gland is collected 
into two masses, one on either side of the intestine ; the oesophagus opens on 
the inferior surface of the intestine, the testis is single, and in most cases the 
vesicula seminalis seems to be double (P. oxycephalum would appear to be an 
exception). 

It would seem only reasonable to suppose that such an amount of difference 
in structure ought to be anatomically expressed by at least a generic difference ; 
but further investigations into the anatomy of other members of the group 
are very desirable to show whether they agree in the possession of these 
characters. 

With respect to the names which these divisions should have, I do not 
think it possible to improve upon those suggested by Leuckart. As van 
i Beneden has pointed out,t Linguatula has a claim to recognition on the score 
of priority, having been applied by Frohlich \ in the case of L. serrata. 

The two genera would then be diagnosed thus, the characters of the family 
remaining as given by Leuckart : — 

Linguatula, Frohlich. 

(Type, Pentastomum tcenioides, Rudolphi. ) 

Body flattened i tody cavity sending out lateral processes into the annuli; hook- 
gland diffuse ; opening of oesophagus into the extremity of the intestine ; testis 
double ; vesicula seminalis single. 

Pentastomum, Rudolphi. 

(Type, P. proboscideum, Rudolphi.) 
Body cylindrical ; body cavity even, without lateral prolongations ; a hook-gland 
on either side of the intestine ; testis unpaired; vesicula seminalis single (?). 

* Van Beneden, Ann. Sci. Nat, s£r. 3 (Zool.) t. xi. p. 313, 1849; Diesing, Ann. des Wien. 
\Mus., Bd. i. p. 1, 1836. 
f Loc. cit., p. 314. 

t Frohlich, Naturforscher, Bd. xxiv. p. 148, 1789 (fide Diesing). 
VOL. XXXII. PART I. 2 H 



100 



MR W. E. HOYLE ON 



EXPLANATION OF THE PLATES.* 

Explanation of Reference Letters the same in both Plates. 



a.g, accessory gland ; a.g', duct of same. 

a.n.c, anterior nervous commissure. 

c.s, cirrus sac. 

cu, cuticle. 

c.z, " Chitinzapfen." 

ep, epidermis. 

g.o, genital openings. 

h.g, hook -gland ; h.g', duct of same. 

i, intestine. 

me, mesentery. 

ml, longitudinal muscles. 

m.o, oblique muscles. 

m.t, transverse muscles. 

n, nerves. 

n.g, nerve ganglion. 

nu, nucleus of sarcolemtna. 

ce, oesophagus. 



o.d, oviduct. 

o.p, oral papilla. 

ov, ovary. 

par, subepidermic cellular layer. 

p.c, parietal cells. 

r.s, receptaculum seminis. 

s.c, stigmatic cells. 

t, testis. 

v, vagina. 

v.d, vas deferens ; v.d', ccecal portion of same. 

v.s, vesicula seminalis. 

u.e, extensor unci muscle. 

u.f flexor unci muscle. 

u.f.a, flexor accessorius unci muscle. 

u.r, retractor unci muscle. 

u.b.a, adductor basis unci muscle. 

u.b.p, protractor basis unci muscle. 



Fig. 


1.- 


Fig. 


2- 


Fig. 


3.- 


Fig. 


4.- 


Fig. 


5.- 


Fig. 


6.- 


Fig. 


7.- 


Fig. 


8.- 


Fig. 


9.- 


Fig. 


10.- 


Fig. 


11.- 


Fig. 


12.- 


Fig. 


13. - 


Fig. 


14.- 


Fig. 


15.- 


Fig. 


10.- 


Fig. 


17.- 



Plate XXVIT. 
Muscles, Digestive and Seceetory Okgans. 

View of Pentastomum protelis, ventral surface (small male specimen). 

Surface view of the cuticle. 

Hooks : I, lateral ; m, median. 

Side view of oral papilla. 
—Transverse section of intestine and mesenteries, with posterior portion of testis. 

Transverse sections of oesophagus. 

■Transverse section of rectum. 

•Median longitudinal section of head. 

Transverse section of body-wall. 

•Transverse section of body, posterior to union of vas deferens and vesicula seminalis. 

•Stigmatic cells. 

Muscles of hook. 
—Transverse section near the posterior extremity. 
—View of transverse muscles. 

Large glandular cells from the body-wall. 
—Terminations of muscular fibres in the cuticle. 

Arrangement of muscles are seen from within the body-cavity. 



* The drawings were (<<y the most pail made by the aid of the camera with Zeiss' microscope. The 
magnifying power employed is marked on the plate beside every drawing. 



A NEW SPECIES OF PENTASTOMUM. 191 

Plate XXVIII. 

Generative Organs. 

Fig. 1. — General view of male organs. 

Fig. 2. — Portion of contents of testicle. 

Figs. 3-7. — Transverse sections of testis at different points as far as the commencement of the 

vesicula seminalis. 
Fig. 8. — Section of vesiculae seminales prior to the separation of the two tubes. 
Fig. 9. — Section of vesiculae seminales after the separation. 
Fig. 10. — Longitudinal section of cirrus sac. 
Fig. 11. — Transverse section of cirrus sac along the line x x. 
Fig. 12. — Transverse section of cirrus sac along the line y y. 
Fig. 13. — Transverse section of accessory gland and duct. 
Fie. 14. — Transverse section of vesicula seminalis, hook-gland, &c. 

Fig. 15. — Transverse section of vas deferens at the point of termination of the vesicula semi- 
nalis. 
Fig. 16. — General view of part of the female organs and nervous system. 
Fig. 17. — Longitudinal section of the receptaculum seminis. 
Fig. 18. — Transverse section of ovary and its mesentery. 



Ioy.Soc.Ediw 



Vol. xxxn. Plate xxvii. 






Fig. 2. 



0. 



T 



% Fzg.7. 



J£ 







7. ■*#* Fig.lt *P 



■ 9 .o. 




Fig I 






FtP.4 ¥ 



c • 



m o. 

m.t. 




Tig. 6. 








Fig.M 



-ipa, r. 




■ 







*# 



cgs^-- 






Fig.16. 



m I. 



Tilt 



' 



Fig. 17. 



Anatomy of Pentastomum proteli 



%* 






Vol. xxxii. Plate xxvii i. 






Fig, 2. 





Fig. 6.-4 










Mi 





Fig. 5 ¥- 




a a.' 




Fig. 10. 




Fig. 9. l '- s - ¥ 



Fig. 11 




Fig. IS 




- 




Fig. 14 




FigJS. 





- OS 



~LO. 






Fig te. 



Fig. 18. 



:-.-■■; 



Anatomy of Pentastomum protelis 



193 



XI. — On Superposed Magnetisms in Iron and Nickel. By Professor C. G. 

Knott, D.Sc. (Plate XXIX.) 

(Bead 2nd July 1883.) 

The experiments which form the subject of this paper are designed, in the 
first place, to test the relation pointed out by Maxwell* between Joule's 
discovery of the lengthening of iron in the direction of magnetisation, t and 
Wiedemann's later researches into the twisting of iron under the influence of 
longitudinal and circular magnetisations,! and, in the second place, to investi- 
gate the corresponding properties of nickel. 

According to Joule's discovery, an iron bar or wire lengthens in the direc- 
tion of magnetisation, and contracts in directions at right angles thereto. 
The extension is greater for a stronger magnetising force, and, if the metal is 
subjected to traction in the direction of lengthening, is smaller for a greater 
traction. In the experiments to be described a wire was fixed at its upper 
end, and stretched vertically by means of an appended mass. It passed cen- 
trally through a glass tube of nearly the same length, round which a helix of 
wire was wound. The length of the helix was 343 centimetres, and the total 
number of coils 196. A current passed through the helix magnetised the wire 
longitudinally. At the lower end of the wire was fixed a short copper wire, 
which dipped into a pool of mercury. By this means a current could be passed 
along the wire so as to magnetise it circularly. The twist produced under the 
joint influence of the longitudinal and circular magnetisations was measured by 
the deflection of a spot of light focussed upon a millimetre scale after reflection 
from a mirror attached to the lower end of the wire. Both the magnetising 
currents were measured on a Helmholtz tangent galvanometer. 

The method of experimenting was as follows : — One of the currents was 
kept steady, while the other was varied through a considerable range. When 
both currents were flowing the free end of the wire came to rest in a definite 
position, which was registered by the reading en the scale. One of the currents 
was then reversed, and a second reading obtained. The difference between 
these readings was approximately four times the angle of twist. By successive 

* See Maxwell's Electricity and Magnetism (2nd edition, vol. ii. § 448). The first edition comesto 
a wrong conclusion, in consequence of a misprint in Wiedemann's Galoanismus (1st edition, Bd. ii. § 491). 
See also Cheystal's article on "Magnetism" in the Encyclopcedia Britannica (vol. xv. pp. 269, 271). 

+ Sturgeon's Annals of Electricity, vol. viii. p. 219 ; and Phil. Mag., 1847. 

\ Wiedemann's Galoanismus, 1st edition, Bd. ii. § 491. 

VOL. XXXII. PART I. 2 I 



194 



PROFESSOR C. G. KNOTT ON THE 



reversings and re-reversings of the current, a series of readings was obtained 
whose differences gave a good mean. From the numbers so deduced the true 
twist expressed in radians was easily calculated. 

The first experiments were made with an iron wire, '00435 square centi- 
metres in cross section. The most important are those in which the current 
along the wire (the linear current) was kept constant, while the helical current 
was made to vary from under half an ampere to nearly six amperes. Five 
different series were taken with different values of the steady current. In the 
following tables the upper row gives the successive values of the helical cur- 
rents in amperes, and the lower the corresponding twists in radians x 10 5 . 



Group A. 
Experiment T. Linear Current = "575 Amp. 



Helical Current, 



Twist, 



0-377 



234 



0-741 



489 



1-289 



629 



2-045 



672 



2-573 



663 



5-019 



625 





Experiment II. Linear Current = 


= -723. 








Helical Current, 


0-368 


0-758 


1-289 


1-676 


2-025 


2-436 


2-902 


3-375 


5019 


Twist, 


307 


597 


816 


877 


907 


900 


881 


832 


703 




Experiment III. Linear Current = 


= 1-891. 









Helical Current, 



Twist, 



0-393 



0-741 



372 



762 



1-254 



1-566 



1179 



1335 



1-987 



1389 



2488 



1389 



2-925 



1387 



3-527 



1345 



4-068 



5-781 



1279 



1077 



Experiment IV. Linear Current = 3-157. 



Helical Current, 


0-460 


0-700 


1-254 


1-991 


2488 


3-157 


4-592 


Twist, 


342 


775 


1251 


1567 


1680 


1710 


1652 



SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 



195 



Experiment V. Linear Current = 4 - 068. 



Helical Current, 


0-410 


0-700 


1-254 


1-891 


2-385 


3-039 


4-214 


Twist, 


390 


810 


1303 


1678 


1802 


1886 


1884 



Three series were taken with steady helical current and varying linear 
current. They are as follows : — 

Group B. 
Experiment I. Helical Current = '611 Amp. 



Linear Current, 


0-410 


0-716 


1-272 


1-943 


2-395 


3-051 


3-899 


Twist, 


126 


357 


742 


1030 


1125 


1197 


1225 



Experiment II. Helical Current = 1-987 Amp. 



Linear Current, 


0-418 


0-750 


1-276 


1-948 


2-364 


2-970 


3-803 


Twist, 


127 


312 


767 


1190 


1358 


1576 


1754 



Experiment III. Helical Current = 3-229. 



Linear Current, 


0-505 


0-893 


1-320 


1-703 


2-724 


Twist, 


152 


387 


718 


877 


1367 



In both these series the wire was under a tension of 1950 grammes' weight. 
The representative curves are shown on Plate XXIX., iron groups A. and B. 
The current strengths of the varied current are laid clown horizontally, and 
the corresponding twists vertically. The two series differ markedly, the 
A group showing a maximum twist for an intermediate current strength, the 
B group giving no such indication. That such a difference between the two 
cases should exist is not to be wondered at, since the magnetisation due to a 



196 



PROFESSOR C. G. KNOTT ON THE 



linear current follows a different law from that due to a helical current. Indeed, 
it is impossible to magnetically saturate an iron wire by means of a linear 
current. Further than this, experiments of the B type need no discussion. 

The maximum point in the curves of group A is a constant characteristic 
of all similar cases, as will be seen by reference to the curves of groups C and 
D. These represent further experiments with iron wires, in which is studied 
more particularly the effect of tension upon the amount of twist. In the fol- 
lowing tables there are three distinct series under each experiment correspond- 
ing to three different tensions. The last column contains the tensions expressed 
in grammes' weight. 



Group C. — Cross Section of Iron Wire = "00276 sq. cc. 
Experiment I. Linear Current = "533 Amp. 



Helical Current, 


0-952 


1-657 


2-489 


3-039 


3-723 


5-198 


Tension. 


( 


561 


632 


632 


607 


523 


413 


1360 


Twist, . .< 


1013 


1148 


1161 


1097 


1013 


875 


712 


( 


1123 


1284 


1258 


1265 


1097 


923 


388 



Experiment II. Linear Current = L476 Amp. 



Helical Current, 


0-533 


0-952 


1-657 


2 489 


3-039 


3-723 


5-198 


Tension. 


( 


484 


1213 


1471 


1484 


1406 


1299 


1097 


1360 


Twist, . .< 


458 


1077 


1452 


1594 


1529 


1426 


1187 


712 


1 


439 


1045 


1503 


1658 


1684 


1561 


1323 


388 



Experiment III. Linear Current = 2 -41 2 Amp. 



Helical Current, 


0-533 


0-952 


1-657 


2-489 


3-039 


3-723 


5-198 


Tension. 


Twist, . -0< 


0484 
0490 
0394 


0877 
1187 
0923 


1332 
1742 
1394 


1445 
1974 
1723 


1510 

1974 
1820 


1555 
2019 
1800 


1394 
1800 
1645 


1360 
712 
388 



SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 



197 



Group D. — Cross Section of Iron Wire = "000714 sq. cc. 
Experiment I. Linear Current = 0'65 Arnp. 



Helical Current, 


0-508 


0-995 


1-593 


2-262 


2-615 


3-157 


4-068 


Tension. 


( 


103 


290 


368 


348 


336 


329 


265 


388 


Twist, . .< 


142 


400 


613 


619 


613 


574 


484 


258 


1 


129 


484 


697 


761 


787 


761 


723 


129 



Experiment II. Linear Current = 0-973 Amp. 



Helical Current, 


0-508 


0-995 


1-593 


2-262 


2-615 


3-157 


4-068 


Tension. 


( 




... 


794 


839 


865 


807 


774 


388 


Twist, . .< 


... 


... 


923 


1090 


1077 


1013 


884 


258 


( 


252 


613 


916 


1045 


1123 


1084 


1045 


129 



The direction of twist was as found by Wiedemann. If the current is 
passed doAvn the wire from the fixed to the free end, and the wire is mag- 
netised with north pole downwards, the free end, as looked at from above, 
twists in the direction of the hands of a watch. As pointed out by Maxwell 
and Chrystal, this agrees with Joule's discovery mentioned above. For the 
circular magnetisation due to the down current is right handed with reference 
to the current. Hence the resultant magnetisation lies in a direction inter- 
mediate to the circular and longitudinal magnetisations at any point ; and as 
the iron extends in the direction of magnetisation, and contracts at right angles 
thereto, there will be a lengthening of the wire in a direction oblique to the 
axis, such as to cause a twist in the direction specified. The amount of twist 
depends not only on the magnetising force in this oblique direction, but also 
upon the obliquity, so that a maximum twist for an intermediate value of the 
helical current is quite in accordance with Joule's result that the extension 
increases with the magnetisation. Suppose, for example, that the circular and 
longitudinal magnetisations at a point on the wire are a and fi, and that these 
give a resultant magnetisation */a 2 + /3 2 in a direction making an angle, whose 
tangent is a//3, with the vertical line through the point. Let the extension 
along this direction be represented by/x (a 2 +/3 2 ), an assumption approximately 



198 



PROFESSOR C. G. KNOTT ON THE 



true according to Joule's researches. Then the amount of twist per unit 
length of the wire will be 

T = ^(a a + j8>/j8 = /*(a 8 /j3 + aj8) . 

If a is constant, t has a maximum value when 

If jB is constant, there is no such maximum value of r. A comparison of curves 
A and B (Plate XXIX.) bear this out fully. 

Hence, in the case of constant circular magnetisation and varying longi- 
tudinal magnetisation, the twist will first increase and then diminish as the 
latter is increased to its saturation point. For a stronger circular magnetisa- 
tion the maximum point is pushed further on, until, when the circular 
magnetisation has reached the saturation point, there will be no subsequent 
fall off in the twist, i.e., no true maximum point. These remarks apply strictly 
to a thin iron cylinder. In the case of a wire the effects are complicated. 
Still the curves on Plate I. bear out in a remarkable way these conclusions. 
Thus in fig. A the maximum point obviously occurs further to the right in the 
higher curve. In the following table a direct comparison between the linear 
current strength and the helical current strength, which corresponds to the 
maximum twist, is established : — 



Linear Current, ..... 
Helical Current for Maximum Twist, 


0-575 
2 


0723 

2-2 


1-891 
2-4 


3157 
3-1 


4-068 
3-5 + 



The highest curve has no distinctly marked maximum, a result in close agree- 
ment with the foregoing deductions. The other series of curves bear out the 
same conclusion. 

Joule also found that the extension for a given magnetisation was smaller 
when the wire was subjected to a greater tension. Hence, in general, we 
should expect the twist in a wire due to superposed circular and longitudinal 
magnetisations to be less for the greater tension, since the longitudinal exten- 
sion will be diminished. This conclusion is quite borne out by curves C and 
D. .With only one exception (namely, C III.) an increase in tension is 
accompanied by a decrease in twist. This result is not in accordance with 
Wiedemann's, who found the twist to be nearly independent of the tension. 
Possibly, however, he worked with a thickness of wire which for the special 
combination of current strengths and tensions was not sufficiently sensitive to 
the change of tension. A glance at the curves C and D shows how much 
greater is the sensitiveness to tension change for certain combinations than for 
others. 



SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 



199 



Joule further discovered that when the tension exceeded a certain value, 
there was contraction instead of extension in the direction of magnetisation. 
This ought to give in these experiments a reversed twist under tensions higher 
than this critical value. Of this, however, there was no indication, although 
the thicker iron wire broke under a tension of 2600 grammes' weight, and was, 
therefore, subjected in experiments A to a comparatively high tension. 

It remains now to consider nickel. The experiments were conducted in 
precisely the same manner as in the case of iron. The following are the 
tabulated results for a nickel wire of cross section, -0056 sq. cc, length 36 cc, 
and tension 1950 grammes' weight ; first, for a steady linear current and varied 
helical current, and second, for a steady helical current and varied linear cur- 
rent. As before, the currents are in amperes, and the twists in radians x 10 5 . 

Group A. (Linear Current Steady.) 
Experiment I. Linear Current = - 674 Amp. 



Helical Current, 


0-368 


0700 


1-210 


1-891 


2-303 


2-616 


3-016 


3-997 


Twist, 


109 


200 


429 


765 


952 


1077 


1206 


1458 



Experiment II. Linear Current == 0995 Amp. 



Helical Current, 


0-307 


0-410 


0-741 


1-276 


1-680 


2-084 


2-594 


5-384 


Twist, 


55 


103 


281 


570 


871 


1052 


1303 


1897 



Experiment III. Linear Current = 2 - 510 Amp. 



Helical Current, 


0-368 


0-700 


1-210 


1-891 


2-303 


2-616 


3-016 


3-997 


Twist, 


152 


263 


596 


1119 


1415 


1923 


2145 


2552 



Experiment IV. Linear Current = 3-039 Amp. 



Helical Current, 


0-205 


0-393 


0-741 


1-313 


1-726 


2-084 


2-594 


3-591 


5-384 


Twist, 


90 


74 


436 


948 


1310 


1553 


1894 


2345 


2819 



200 



PROFESSOR C. G. KNOTT ON THE 



Experiment V. Linear Current = 4"441 Amp. 



Helical Current, 


0-205 


0-451 


0-783 


1-298 


1-750 


2-084 


2-594 


3-565 


5-479 


Twist, 


123 


219 


584 


1145 


1535 


1797 


2126 


2626 


3152 



Experiment VI. Linear Current = 5-578 Amp. 



Helical Current, 


0-3G8 


0-576 


0-952 


1-521 


1-938 


2-784 


4-519 


Twist, 


171 


345 


855 


1442 


1736 


2268 


2987 



Group B. (Helical Current Steady.) 
Experiment I. Helical Current = - 658 Amp. 



Linear Current, 


0-368 


0-578 


1-097 


1-815 


2-368 


2-724 


3-277 


3-815 


4-796 


Twist, 


39 


74 


132 


234 


383 


505 


702 


897 


1019 



Experiment II. Helical Current = 1-891 Amp. 



Linear Current, 


0-327 


0-582 


1-141 


1-891 


2-891 


3-463 


3-927 


5-019 


Twist, 


57 


89 


180 


420 


954 


1371 


1700 


1991 



Experiment TIL Helical Current = 2-702 Amp. 



Linear Current, 


0-327 


0-582 


1-141 


1-891 


2-891 


3-463 


3-927 


5-019 
2322 


Twist, . 


29 


89 


216 


457 


1126 


1545 


1948 



SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 



201 



Experiment IV. Helical Current = 2-405 Amp. 



Linear Current, 


0-893 


1-520 


2323 


2-812 


4-334 


4-680 


Twist, 


368 


819 


1355 


1561 


1865 


1890 



Experiment V. Helical Current = 3*338 Amp. 



Linear Current, 


0-867 


1-494 


1-797 


2-298 


2-702 


3-277 


4-519 


Twist, . 


439 


929 


1226 


1639 


1909 


2168 


2374 



The representative curves are shown on Plate XXIX., nickel groups 
A and B. The chief points of difference between the behaviour of iron and 
nickel are these: first, the direction of twist in the nickel is the reverse of that 
in the iron; and second, there is no maximum in the nickel A group of curves. 
The free end of the nickel wire twists in the direction opposite to the hands 
of a watch, as looked at from above, when the wire is traversed by a down 
current, and is magnetised with north pole downwards. This agrees with 
Barrett's discovery,* that nickel contracts when magnetised. The jjossibility 
of a maximum, again, depends upon how the amount of contraction varies 
with the magnetisation, and also, since the abscissae represent currents and not 
magnetisations, upon the relation which holds between these last. 

The B curves are very similar in form to the B curves of the iron. It will 
be noticed that curve IV. of this series lies for the most part higher than curve 
III., although the steady helical current is smaller in the former; also that I., 
II., and III. seem to fall together, as belonging to the same set, while IV. and 
V. form a system by themselves. The reason of this would seem to be that 
between the dates, June 2nd and 4th, namely, on which these sets were taken, 
the nickel wire underwent some physical change. Probably this was of the 
nature of a change in temper, since on the latter date the nickel wire was for 
1 an instant traversed by a current of sufficient strength to make it glow red hot. 
Taking this consideration into account, and neglecting curve A, III., which is 
obviously a bad experiment, we conclude that the twist due to the superposi- 
tion of circular and longitudinal magnetisations in nickel wire increases with 



* See Nature, vol. xxvi. 1882. 



VOL. XXXII. PART I. 



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( 205 ) 



XII. — On the Relative Electro-Chemical Positions of Wrought Iron, Steels, 
Cast Metal, &,c, in Sea- Water and other Solutions. By Thomas Andrews, 
Assoc. M. Inst. C.E., F.C.S. (Plates XXX. to XXXIV.) 

(Read 15th January 1883.) 

The experiments contained in this memoir were made by the author with 
the galvanometer on wrought iron, steel, cast metal, &c, bars and plates, 
arranged in galvanic circuit in sea- water and various other waters and solutions, 
to determine the relative electro-chemical position of these metals under such 
circumstances. 

These varieties of the same metal iron are of such vast and universal utility 
that accurate information respecting any of the properties possessed by them 
cannot fail to be of interest. 

A knowledge of the relative electro-chemical positions assumed by wrought 
iron, steels, and cast metal when in galvanic connection in sea-water is of 
importance as determining their respective liability to electrolytic disintegration 
when combined in marine works and structures, and a research of this kind 
presents features of interest capable of practical application in many ways. 

When plates or bars of wrought iron, steel, &c, are connected in circuit 
and immersed in sea-water or other solution, and attached to a delicate galva- 
nometer, an electric current is set up of varying power according to the 
difference of chemical composition or mechanical or physical projDerties, &c, of 
the wrought iron and steels employed. 

The following experiments were undertaken by the author to measure, if 
practicable, the extent of this action, and to endeavour to determine the relative 
electro position of the various steels, wrought iron, and cast metal, with some 
degree of exactness. 

Table A. 

Analyses of Steel, Wrought and Cast-Iron Bars. Percentage Composition. 



Description. 


Graphitic 
Carbon. 


Combined 
Carbon. 


Silicon. 


Sulphur. 


Phosphorus. 


| 

Manganese. 


Tun 


gsten. 


Iron 
(by difference). 


Soft Siemens- Martin stee 


1, ... 


















Wrought iron, 




Trace 


•224 


None 


•239 


•071 






99-466 


Soft steel (Firth's), . 




•570 


•032 


Trace 


•066 


•147 






99-185 


Bessemer steel, 




•550 


None 


•032 


•175 


•216 






99-027 


Puddled steel, 




•440 


•144 


•048 


•149 


Trace 






99219 


Puddled steel (chilled), 




•490 


•140 


•004 


•073 


•215 






99-078 


Hard steel (Firth's), 




1-600* 


■145 


•002 


•025 


•183 






98-045 


Cast metal, 


2-400 


1-000* 


•570 


•140 


•580 


•860 






94-450 


Tungsten steel, 




1-750* 


•135 


•069 


•139 


■720 


9- 


270 


87-917 



By combustion. 



VOL. XXXII. PART T. 



2 L 



200 



MR THOMAS ANDREWS ON THE RELATIVE 



One interesting fact observed in the course of these experiments is that 
■wrought iron and steels, &c, are not static in their relative electro-chemical posi- 
tions, and when immersed in sea-water, or other solutions in connection with each 
other, cannot exactly be regarded as constant elements. The relative electro- 
chemical position is also varied, according to the nature of the solutions employed. 

The chemical composition of the iron and steel bars and plates employed in 
the following experiments is shown by the accompanying analyses. 

Table B. 

Analyses of Steel, Wrought and Cast-iron Plates. Percentage Composition. 



Description. 


Graphitic 
Carbon. 


Combined 
Carbon. 


ilicoii. 


Sulphur. 


Phosphorus. 


Manganese. 


Iron 
(by diffeienee). 


Soft Siemens-Martin steel, 




■170 


071 


•117 


•077 


•627 


98-938 


Soft steel (Firth's), . 




•460 


074 


•025 


•210 


•184 


99-047 


Wrought iron, 




Trace. 


•206 


•024 


•454 


•396 


98-920 


Soff Bessemer, 




•150 


•015 


•111 


•064 


•540 


99-120 


Hard Bessemer, 




•510 


•068 


•113 


•087 


1-153 


98 069 


Hard Siemens-Martin steel, . 




•720 


•080 


■102 


•143 


1-239 


97-716 


Hard steel (Firth's), 




1-407* 


•121 


•056 


■080 


•360 


97-976 


Cast metal, .... 


1-500 


2-010* 


•410 


•250 


•450 


•650 


94-730 



* By combustion. 



Some of the physical properties of the bars employed are indicated by the 
following tests to which they were submitted : — 



Table C. 



Description 


Original. 


Ultimate Stress. 


Fractured. 


Stress 
per Square 

Inch of 
Fractured 

Area. 


Extension 
in 10 Inches. 


Appearance 

of 

Fracture. 


Size. 


Area. 


Total. 


Per Square Inch 
of Original Area. 


Size. 


Area. 


Difference. 


Inch. 


Per 

Cent. 


Area 


Per 

Cent. 


Tungsten steel, 

Hard steel, 

Bessemer steel, 

Puddled steel, 

Puddled steel ) 
(chilled), ] 

Wrought iron, 

Soft Siemens- ) 
Martin steel, \ 

Cust metal, 


Inch. 
•30 

•298 
•297 
•296 

•298 

•296 

•38 

•293 


Sq. in. 

•070 

•0697 
•0693 
•0688 

•0697 

•0688 

•113 

•0674 


lbs. 
12,561 

10,967 
9,851 
7,180 

6,322 

6,028 

8,328 

1,436 


Lbs. Tons. 

179,443 = 80-1 

157,346 = 70-2 
142,150 = 63-4 
104,361=466 

90,703 = 40-5 

87,618 = 39-1 

73,699 = 329 

21,305= 9-6 


Inch. 
•27 

•289 
•275 
•257 

•295 

•284 

•25 

•293 


Sq. in. 
•057 

•0656 
•0594 
•0518 

•0683 

•0633 

•049 

•0674 


■013 

•0041 
•0099 
•0170 

■0014 

•0055 

•064 

•0000 


18-6 

5-8 
14-2 
24-7 

2-0 

7-9 

566 

o-o 


lbs. 
220,368 

167,179 
165,841 
138,610 

92,562 

95,229 

169,959 

21,305 


73 

•12 
•16 

•27 

•07 

■11 

1-97 

•00 


7 3 

1-2 
1-6 

2-7 

0-7 

1-1 

19-7 

o-o 


( 10 % silky 
\ 90 % granular 

100 % granular 

100 % granular 

100 % silky 

( 35 % silky 
\ 65 % granular 

100 % fibrous 

100 % silky 

( 100 % granular 
I (mottled) 









A 
< 3" ;-■--> 

"in 





ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON", ETC. 207 

Galvanometer Experiments. 

The bars of wrought iron and steels, &c, used in the experiments were 
exactly T 2 <y 9 ^jths of an inch (7*5 millimetres) in diameter, and were cut as test 
pieces from near the centre of bars of wrought iron and steel, manipulated as 
near alike as possible for purposes of comparison. 

All the wrought iron and steel, &c, plates employed in 
the following experiments, except where otherwise de- 
scribed, were exactly three inches square (representing a 
total surface area of exposure of eighteen square inches 
for each plate, exclusive of the edges which were alike 
in each case), and were of uniform thickness, and in shape 
as shown in fig. No. 1. 

The bars and plates were of the chemical composition and Fig, l. 

possessed of the general physical properties, as shown in the preceding tables, 
and with the exception of those covered with scale (magnetic oxide), were 
all smoothly polished bright. 

The experiments on the various samples were conducted in each case in 
precisely the same manner for purposes of exact comparison, and very many 
times repeated, but in the same manner for corroboration, the results being 
derived from exactly corresponding experiments in each case, the bars and 
plates in the solutions being kept exactly the same distance apart, &c, in fact, 
every precaution was adopted to insure accuracy. 

The records in the following tables of galvanometer experiments are the 
result of some 3000 carefully made observations by the author, some of which 
were thirty or forty times repeated to insure accuracy. 

It should be understood that the following experiments do not represent 
fixed or permanent deflections ; but they are the results of a number of observa- 
tions made in precisely the same manner in each case for purposes of exact 
comparison between the various steels employed. 

In cases where necessary the author has recorded the highest and lowest 
deflection noticed, in addition to the averages to illustrate the variations better. 
In the galvanometer experiments the bars and plates were all immersed, one 
pair at a time, in an equal measured quantity of sea- water, or other solutions, 
and placed in galvanic connection at equal distances apart. The wrought iron, 
&c, bar or plate, was connected with one terminal of a delicate galvanometer, 
to the other terminal of which was attached the bar or plate of steel, &c. The 
connections were made with insulated copper wires properly secured to the ends 
of the bars or plates with screw clips. 

The measurement of the galvanic action is recorded in the tables. 

[Inserted April 5, 1883. — The galvanometer selected for these experiments 



208 MR THOMAS ANDREWS ON THE RELATIVE 

was a low resistance galvanometer, with jewelled centre, accurately graduated 
throughout the circle. 

To observe the fractional parts of degrees with accuracy, the author took 
the observations through a powerful lens fixed above the galvanometer, by 
means of which arrangement and from the author's experience in using it in 
this manner, and from repeated check experiments, it was found that variations 
of the needle could be taken to about the -f^th of a degree of deflection. 

The galvanometer was examined by the Wheatstone Bridge arrangement 
with standard resistance coils, and the resistance was found to be 220 ohms. 

A Daniells cell through a resistance of 9180 ohms (including the resistance 
of the galvanometer) gave a deflection of one degree, or ^ T Voth of an ampere 
produces a deflection of one degree (taking the electromotive force of the 
Daniells cell as unity). 

From these observations, therefore, the strength of the electric current 
represented by the deflections recorded in this paper may be calculated ; and 
as the resistance in the cells containing the sea- water would not exceed 
3 ohms, an indication of the E.M.F. can be obtained. 

In taking all readings the galvanometer was very carefully adjusted before 
each observation, and all deviations from vibration, tremor, or other causes, 
carefully guarded against; the greatest care was exercised in the experiments, 
the point of the needle being under constant observation, and the slightest 
variations were carefully watched as the differences to be dealt with in course 
of these experiments were sometimes small. 

The author is satisfied that the observations recorded represent accurately 
differences arising from the nature of the metals and solutions employed.] 

The experiments on bars, recorded in tables D, E, F, represent the average 
of the deflections observed on first immersion of the steel and iron bars in the 
sea-water, the bars on each repetition of the experiment being carefully washed 
and wiped dry before re-immersion. 

A very marked feature in the other galvanometer experiments, recorded in- 
table and diagram G, I, Plate XXXII. (these observations extending over 
longer periods of time), is the steadily changing deflections noticed from the 
commencement; this appears to indicate a tendency in the various steels and 
irons to polarise each other's electric action, so that in course of time, as 
submerged iron and steel becomes coated with oxides, galvanic activity is con- 
siderably reduced from its first force; but it does not wholly subside. When 
plates of iron and steel, &c, in galvanic connection were taken out of the sea- 
water (the oxides being washed off) and were re-immersed, the deflections of 
the galvanometer arose for a time, afterwards reducing Again. 

The experiments in this memoir indicate that the galvanic relationships of 
the various steels and wrought iron do not remain the same, in sea-water or 
Other solutions, but they appear capable of an interchange of electro-chemical 



ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 209 

position; for instance, in the experiment with the plates, some of the steel 
plates took a negative position compared with the wrought iron ; but afterwards 
the position was reversed. 

This change of electro-chemical position is a fact of considerable interest, 
and the author has therefore given as typical some of the full records of the 
deflections observed in some of the experiments between steels, wrought iron, 
cast metal, &c. 

These diagrams, &c, illustrate this tendency in detail. A reference to some 
of the tables will also show that in many instances the interchange is greatly 
varied and influenced by the nature of the solutions in which the steels, &c, 
were immersed. When the steels, &c, were immersed in an acid solution 
instead of one containing neutral salts, such as sea-water, a noticeable result 
was, in some instances, an almost complete reversal of electro-chemical position. 
(See table and diagram G, I, Plate XXXII.) 

Although the soft steel and Bessemer steel bars in table D are recorded 
thereon as in the negative position compared with wrought iron, this is not 
contradictory to the results of similar soft steels in table G, because the results 
in table D are the first deflections, whereas those in table G indicate the same 
negative position at the commencement of the experiment ; but the electro- 
chemical position afterwards changes by prolonged exposure. 

An explanation of this change in the electro-chemical position of the soft 
steels may be that, as the solution gradually penetrates and acts on the metal, 
it meets with crystalline networks of higher carbides, &c, and other consti- 
tuents of varying composition, which would probably offer varying resistance to 
the action of the solution. 

This view of the case would appear to derive support from the observations 
made " On the Microscopical Structure of Iron and Steel," by Henry Clifton 
Sorby, Esq., LL.D., F.R.S., from which it would appear that iron or steel of 
the finest manufacture cannot be regarded as of purely homogeneous composition. 

The experiments recorded in the following tables were made not only with 
the object of endeavouring to ascertain the relative electro-chemical position of 
wrought iron, steels, and cast metal, but also to throw light, if possible, on the 
amount of galvanic action which takes place practically where these metals are 
combined in marine or other structures. It will be seen, therefore, that the 
observations are roughly arranged with this object. 

Amongst other experiments, measurements were not only taken using zinc, 
copper, and wrought iron as standards in combination with iron and steel and 
cast metal, &c, but it will be also observed that bars and plates covered with 
magnetic oxide were employed, as practically the action of this oxide upon 
wrought iron, steels, and cast metal in sea- water, &c, is frequently a source of 
electrolytic disintegration, to ascertain the extent of which forms one object 
of the following experiments : — 



210 



MR THOMAS ANDREWS ON THE RELATIVE 



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ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 



211 



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MR THOMAS ANDREWS ON THE RELATIVE 



Table F. 

Galvanometer Experiments with Bright Steel, Wrought Iron, Cast Metal Bars, $e. 



Description. 


Percentage 
of Com- 
bined 
Carbon. 


SOLUTION IN WHICH THE BARS WERE IMMERSED. 


One-Fifth Normal Standard Sulphuric Acid. 


Zinc Rod forming one 

Element with cacli of 

following. 


Wrought Iron Bar 
forming one Element 
with each of following. 


Iron Scale (Magnetic 

Oxide) forming one 

Element with each of 

following. 


Deflection 
of Galvano- 
meter in 
Degrees. 

1 


Electro- 
chemical 
Position of 
the Metals. 


Deflection 
of Galvano- 
meter in 
Degrees. 


Electro- 
Chemical 
Position of 
the Metals. 


Deflection 
of Galvano- 
meter in 
Degrees. 


Electro- 
Chemical 
Position of 
the Metals. 


Sjft Siemens-Martin steel, 




8-90 


N 


0-62 


P 


14-15 


P 


Wrought iron, 


Trace 


10-10 


N 






1490 


P 


Soft steel (Firth's), .... 


0-570 


8-89 


N 


0-25 


N 


14-87 


P 


Bessemer steel, ..... 


0-55 


9 03 


N 


0-55 


N 


13-80 


P 


Puddled steel, .... 


0-44 


8-08 


N 


0-60 


N 


13-90 


P 


Puddled steel (chilled), . 


049 


9-97 


N 


0-90 


N 


13-77 


P 


Hard steel (Firth's). .... 


1-600 


8-84 


N 


0-57 


N 


14-95 


P 


Cast metal (graphitic carbon, 2'40 ) 
per cent.), ) 


1-00 


12-50 


N 


0-95 


N 


15-07 


P 


Tungsten steel, ..... 


1-75 


9 40 


N 


016 


N 


14-27 


P 



Bemarks. 
Each result is the average of ten observations made in the same manner f >r exact compuison. 



A reference to the analyses of the steel plates s-hows that, as regards 
manufacture, they were selected from three of the most important classes 
of steel, viz., Bessemer, Siemens-Martin, and cast steel, and a sample of the 
softest and hardest temper was taken from each kind. 



ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 



213 



Table G. 

Galvanometer Experiments with Bright Steel, Wrought Iron, and Cast Metal Plates, §i 



Description. 


Percentage 
of Corn- 
Dined 


WATERS IN WHICH THE PLATES WERE IMMERSED. 


Sea-Watek. 


Wrought Iron Plates (Bright) forming 

one Element with each of the 

following Bright Steel, <&c. Plates. 


Plates covered with'Scale (Magnetic 

Oxide) placed in Galvanic connection 

with Bright Plates from the same 

Piece of Steel, &c. 






Deflection of 

Galvanometer in 

Degrees. 


Electro-Chemical 

Position of the 

Metals. 


Deflection of 

Galvanometer in 

Degrees. 


Electro-Chemical 

Position of the 

Metals. 














Average. 


Highest. 




Vverage. 


Highest. 




Soft Siemens-Martin steel, . 


' 0-170 


2-69 


3 00 


N 


.3-51 


4-00 


P 


Soft steel (Firth's), 


0-46 -i 


1-25 

0-77 


1-50 
2-25 


N for 3 minutes, 
afterwards P to 
end of Experi- 
ment 


>3-27 


375 


P 


Wrought iron, .... 


Trace 


... 






2-92 


3-00 


P 


Soft Bessemer, . . 


0-150 ) 


0-37 

0-83 
0-28 


0-50 
2-75 
0-50 


N for 3 minutes 
P for 120 „ 
N afterwards 


U-96 


5-00 


P 


Hard Bessemer, .... 


0-510 1 


1-05 
0-75 


1-50 
1-25 


Nfor 20 minutes 
P afterwards 


\ 3-27 


4-25 


P 


Hard Siemens- Martin steel, . 


0-720 ] 


1-25 
0-14 
0-15 


1-50 

0-25 
0-50 


Nfor 10 minutes 
P for 85 „ 
N afterwards 


( 2-58 


3-75 


P 


Hard steel (Firth's) . 


1-407 \ 


1-06 
0-21 
012 


1-75 

0-50 
0-15 


Nfor 15 minutes 
P for 80 „ 
Nfor 55 „ 


il-63 


3-75 


P 


Cast metal,* 


2-010 


1-50 

t 


2-00 


F { 


0-93 

0-47 

■*- 

4- 


2-75 
0-60 


Nfor 30 minutes 
P afterwards 



Graphitic carbon, 1'50. 



Eemarks. 



t Each result is the average of about thirty observations which were taken at regular intervals extending 

over three hours. 
X Each result is the average of twenty-three observations taken in each case at equal distances of time, 

each experiment extending over two hours. 



VOL. XXXII. PART I. 



2 M 



214 



Mil THOMAS ANDREWS ON THE RELATIVE 



Table H. 

Galvanometer Experiment* with Copper, Steel, Wrought Iron, and Cast-Metal Plates, #c 



Description 


Percentage of 

Combined 
Carbon. 


WATER IN WHICH THE PLATES WEUE IMMERSED. 


Ska-Watkr. 


Copper Plate (Bright), forming one Element with each of the 
following Bright Steel, &c, Plates. 


Deflection of Galvanometer in Degrees. 


Elect ro- 
Cliemical Posi- 
tion of the 
Metals. 


Average. 


Highest. 


Lowest. 


Soft Siemens-Martin steel, 


0170 


6-17 


9-50 


4-50 


P 


n Soft steel (Firth's), .... 


0-460 


6-15 


9-00 


4-25 


P 


Wrought iron, ..... 


Trace 


8-62 9-75 


4-50 


P 


Soft Bessemer, ..... 


0-150 


6-74 


9-50 


5-25 


P 


Hard Bessemer, .... 


0-510 


7-33 


975 


5-40 


P 


Hard Siemens-Martin steel, 


0-720 


7'25 


9-50 


5 - 75 


P 


Hard steel (Firth's), .... 


1 -407 


7-05 


8-00 


5-50 


P 


Cast metal,* 


2-01O 


7-26 


10-50 


5-75 


P 



* Graphitic carbon, 1 -50 per cent. 



Remarks. 

Each of the above results is the average of nineteen observations, each taken at e<jual d stances of time, 
each experiment extending over three hours. 



ELECTRO-CHEMICAL POSITIONS OF WROUGHT-IRON, ETC. 



215 



Table I. 

Galvanometer Experiments with Bright Steel, Wrought Iron, and Cast-Metal Plates, Sfc. 



Inscription. , 


Percentage 

of Combined 


SOLUTION IN WHICH THE PLATES WERE IMMERSED. 


One-Fifth Normal Standard Sulphuric Acid. 


Wrought-Iron Plates {Bright), forming 

one Element with each of the following 

Bright Steel, &c, Plates. 


Plates covered with Scale (Magnetic 

Oxide) placed in Galvanic Connection 

with Bright Plates from the same 

piece of Steel, &c. 






Deflection of 

Galvanometer in 

Degrees. 


Electro-Chemical 

Position of the 

Metals. 


Deflection of 

Galvanometer in 

Degrees. 


Eleetro-Chemical 

Position of the 

Metals. 














Average. 


Highest. 




Average. 


Highest. 




Soft Siemens-Martin steel, 


0-170 | 


0- 7 
0.0 


2-25 
1-00 


P for 26 minutes 
N afterwards 








Soft steel (Firth's), . 


0-460 | 


0-25 
1-00 


0-25 
1-25 


P for 2 minutes 
N afterwards 








Wrought iron, .... 


Trace 














Soft Bessemer, .... 


0-150 j 


0-40 
0-24 


2-00 
0-25 


P for 60 minutes 
N for 120 „ 








Hard Bessemer, 


0-510 


1-21 


1-75 


P 








Hard Siemens-Martin steel, 


0-720 


1-62 


2-00 


P 








Hard steel (Firth's), . 


1-407 


0-74 


2-00 


P 










r 


0-44 


1-25 


P for 12 minutes 


0-62 


1-00 


P for 5 minutes 


Cast metal,* .... 


2-010 < 


0-63 


0-90 


N afterwards 


0-12 


0-25 


N afterwards 



* Graphitic carbon, 1'50 per cent. 
Remarks. 
Each result is the average of about forty observations, taken at equal distances of time, each experiment 

extending over three hours. 
It is interesting to compare the results of the above table and diagram I with table and diagram G. 
A partial reversal of the galvanic positions of some of the steels appears to take place, when an 
acidsolution is employed instead of sea-water, as previously pointed out. 

Experiments to ascertain the Galvanic Action caused by Plates of Wrought Iron 
{the half of every Plate being Bright, the other half left with its Scale on). 

Eleven plates of wrought-iron (cut from the same large plate) were each 
bent double, thus, the half of every plate polished bright, and the 
other half left covered with scale just as it left the rolls, they were 
then placed in a clean porous cell, Daniells battery, filled with sea- 
water. 

Each plate was 4*12 inches square, and as there were eleven in 
the whole series, this represents a total superficial area of 373-48 Fiw 2 
sq. inches of scaled surface, and 373-48 sq. inches of bright surface, 
though, of course, the action of a voltaic series like this would be different to 



-2h> 



MR THOMAS ANDREWS ON THE RELATIVE 



that of two large plates of sueh superficial area. This arrangement, however, 
illustrates intensified galvanic action. 

The whole were arranged in a voltaic series, as shown in sketch — 



SCALED 
TERMINAL 







( 


-\ 


-> 




f\ 




— ^ 




r> 




p 




r> 


r\ o r* 








Uj 


<<> 










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i 





Fig. 3. 



and attached to the terminals of a galvanometer, the deflections were as 
recorded under 

Table J. 



Time of 
Observation 


Deflection in 
Degrees. 


Electro-Chemical 
Position of Bright Part 


June 


3rd 


, 7.35 
7.40 


17-00 
14-00 


Positive. 


>> 




7.50 


11-00 


!> 


>> 




8.0 


9-00 


)> 


» 




8.10 


7-50 


>J 


>> 




8.20 


6-75 


" 


>i 




8.30 


6-00 


JI 


)) 




8.40 


5-00 


>' 


;> 




8.50 


4-75 


1) 


:; 




9.0 


4-50 


>> 


>) 




9.10 


4-00 


>; 


>> 
)> 




9.20 
9.30 


3-75 
3-50 


J) 


i> 




9.40 


3-25 


» 


» 




9.50 


3-25 


>' 


jj 




10.0 


3-00 


>) 


n 




10.10 


3-00 


>> 


V 




10.20 


2-75 


>> 


J' 




10.30 


2-50 


>t 


i) 




10 35 


2-50 


'.) 


June 


4tb 


> ' 


1-00 






5th 
6th 


> 


TOO 
0-75 


>> 
11 



The galvanic mischief induced by iron scale is a matter of such importance 
that special attention has been directed to the measurement of this, as will be 
seen in these experiments (see Tables). 



ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON", ETC. 



2J7 



• Experiments on the Galvanic Action set up by a series oj B irs of Wrought 
Iron and various Steels immersed in Sea- Water. 

The sample bars were portions cut from the same rods whose composition 
and general properties have been previously described. 

The deflections of the needle of the galvanometer are shown in the accom- 
panying tables K and L. 

Table K. 

Deflection of the Galvanometer Needle, produced when Bars 0/ Wrought Iron and Hard Cast 
Steel (all of the same size and polished bright) were immersed in Sea- Water forming the 
elements of Galvanic Action. Average of eight Experiments in each case.. 





Deflection of Needle. 


3 Bars of 


wrought iron connected 


with 3 Bars of hard cast steel, 


1'28 degrees 


4 „ 


» 




4 „ 


1-38 „ 


5 ,, 


>> 




5 „ 


1-52 „ 


6 „ 


it 




6 „ 


1-75 „ 


7 „ 


>> 




7 „ 


212 


8 „ 


» 




8 „ 


2-25 



The wrought iron was the electro-positive metal. 

Table L. 

Deflections of the Galvanometer Needle produced when Polished Bars of the Wrought Iron anl 
the Soft Steel, the same size, xoere immersed in Sea- Water forming the elements of Galvanic 
Action. Average of six Experiments in each case. 





Deflection of Needle. 


3 Bars of the wrought iron connected with 3 Bars of the soft cast steel, 
^ i) » >> ^ » >> 
" » >> » " >> >} 


TOO degrees 
1-30 „ 
1-33 „ 



The wrought iron was the electro-positive metal. 

The whole of the preceding galvanometer experiments afford some compari- 
son of the galvanic action set up by the exposure of combinations of wrought 
iron, steel, &c, to sea-water, colliery mineral waters, or river waters, &c, of 
known composition, and are so far interesting, because in actual practice 
wrought and cast iron and steel bars, plates, &c, are frequently exposed to 
similar destructive influences. 



218 RELATIVE ELECTRO-CHEMICAL POSITIONS OF WROUGHT IKON, ETC. 

Ill experiments made by the author to ascertain the galvanic action taking 
place between wrought iron and steels, &c, over more extended periods of 
time, it was found that galvanic action between these metals had a tendency 
to be reduced from various causes during prolonged exposure to sea-water and 
other solutions. 

The general deductions from the foregoing observations are that — 

1st, The electro-chemical position of wrought-iron, steels, and cast metal 
appears capable of changing according to the nature of the solution in which 
they are immersed, an acid solution producing frequently different results from 
one containing only neutral salts, This interchange of electro-chemical position 
between the metals being also frequently observable both when immersed in 
an acid and neutral solution, as indicated by the preceding tables. 

2nd, A measurable difference is noticeable in the behaviour of the various 
steels, &c. employed under the conditions recorded in the experiments. This 
would lead to the conclusion that the danger from the greatly increased 
corrosion in sea-water, &c, through galvanic action, is a factor not to be 
disregarded in compound structures of the preceding metals. The tendency to 
polarise each other's action, and the consequent interchange of electro-chemical 
position, would appear to exert a considerable influence in retarding and 
reducing this source of danger. Galvanic action between wrought iron and 
steels, &c, appears (from experiments on hand by the author) also to be 
materially reduced in course of extended periods of time, otherwise the liability 
to destructive corrosion through such action, though never inconsiderable, 
would be a more formidable matter to encounter than in engineering practice 
it really is. At the same time, it need scarce be remarked, this source of dis- 
integration should not be overlooked in constructive works of wrought and 
cast iron and steel. 

It is not now necessary for the author to attempt to enter into the further 
practical application of the results deducible from the experiments contained in 
this memoir ; he has, however, great pleasure in being permitted the honour 
to present the results herein recorded as a contribution to the chemistry of 
iron and steel. 







Soc. EniN R 



DIAGRAM D. 

Illustrating some of the Comparative Results in Table D. 



Plate XXX. 





Waters in which the Bars were immersed. 




Sea Water. 


An Acid Colliery Water. 


[PTION. 


Curves Showing the comparative Electro-Chemical 
positions of the steels, &c 


Curves showing the comparative Electro-Chemical 
positions of the Steels, &c. 




Positive 
position 
of Metals. 


Negative position of Metals. 


Positive 

position 

of Metals. 


Negative position of Metals. 




Degrees of Deflection of Galvanometer. 


Degrees of Deflection of Galvanometer. 




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Soc. Edin r _ _ _ „ 

DIAGRAM 

lustratingihe change of Electro-Chemical position between some 


G. 

Steel and 


Wrought-Iron Plates 


, set 


Plate XXXI. 

j Table G. 


Waters in which the Plates remained constantly 
immersed during the experiment. 


Curve showing the varying Electro-Chemical position of the 
Steels in Galvanic connection with Wrought-Iron. 






Sea Water. 




Plate (bright) forming one 
lard Cast Steel Plate (bright). 


Wrought-Iron Plate (bright) forming one 
element with a Soft Bessemer Plate (bright). 


Time 


Positive position 
of Steels. 


Negative position of 
Steels. 






■alvano- 
grees 
f time 
hours. 


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Hard Cast Steel. 


Deflection of Galvano- 
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Steel. 


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Soc. Edin r 



DIAGRAM G. I. 

'ustraiing the change of Electro-Chemical position between Cast Metal and Wrought- Iron Plates, see Table G 1. 



Plate XXXII. 



Solutions in which the Plates remained constantly 
immersed during the experiment. 


Curve Showing the varying 


E 


lectro-Chemical positioi 


J of the 
Iron. 




Sea Water. 


\t\v Normal Standard Sulphuric Acid. 


Cast Metal in Galvanic connection with wrought- 


n Plate (bright) forming one 
h a Cast Metal Plate (bright). 


Wrought-Iron Plate (bright) forming one 
element with a Cast Metal Plate (bright). 


Time 


Positive position of 
Cast Metal. 


Negative position of 
Cast Metal. 




on of 

in Degrees 
a Is of 


Electro-Chemical 

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Deflection of 
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at intervals of 
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Electro-Chemical 

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The Black Line indicates the deflections caused by the Cast Metal in Galvanic connection with Wrought-Iron in Sea Water. 

Dotted ,, ,, ,, >> »» ii » >> >> >» " " >> .. >> rth Normal Standard Sulphuric Acid. 


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DIAGRAM H. 

'rating the change of Electro-Chemical position between Steel, Wrought-Iron, and Copper Plates, see Table H. 



Plate XXXIII. 



Water in which the Plates kemained constantly 
immersed during the experiment. 


Curve showing the varying Electro-Chemical position of the 






Sea Water. 




bright) forming one element 
iemens-Martin Steel Plate. 


Copper Plate (bright) forming one element 
with a Wrought Iron Plate (bright). 


r 

lime 


Positive position of the Steels. 


Meridian. 






Salvano- 
igrees 
)f time 
hours. 


Electro-Chemical 

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Martin Steel. 


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meter in Degrees 
at intervals of time 
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Electro-Chemical 

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„ „ „ „ Wrought-Iron „ ,, „ ,, ,, „ „ 




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Soc. Edin r 



DIAGRAM I. 

'/ustratingthe change of Electro-Chemical position between some Steel and Wrought-lron Plates, see Table I. 



Plate XXXIV. 



Solution in which the Plates remained constantly 
immersed during the experiment. 


Curve showing the varying Electro-Chemical position of the 
Steels in Galvanic connection with Wrought-Iron. 




£th Normal Standard Sulphuric Acid. 




l Plate (bright) forming one 
Soft Siemens-Martin Steel Plate 


Wrought-lron Plate (bright) forming one 
element with a Soft Bessemer Plate (bright) 


Time 
from 


Positive position of 
Steels. 


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2 

td 




"Galvano- 


Electro-Chemical 

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( 219 ) 




XIII. — Report upon the Tunicata dredged during the Cruises of H.M.SS. 
"Porcupine " and "Lightning,' 1 '' in the Summers of 1868, 1869, and 1870. 
By W. A. Herd man, D.Sc, Professor of Natural History in University 
College, Liverpool. (Plates XXXV. and XXXVI.) 

(Read 7tli January 1884. ) 

A few years ago the late Sir C. Wyville Thomson gave me for examination 
some specimens of Ascidians which had been obtained during the cruises of 
the "Porcupine" and "Lightning," and last summer I received from Mr John 
Murray the remainder of the Ascidise Simplices and two species of the 
Ascidise Compositae from the same deep-sea dredging expeditions.* Some 
additional specimens of the " Porcupine " Ascidiae Compositae have been placed 
in my hands during the last few days (January 1, 1884). The present paper 
contains a detailed account of the Simple Ascidians alone; the Compoum 
forms will be worked up along with the "Challenger" Ascidise Compositae, 
and will be described and figured in the second part of my Report upon the 
Tunicata of the "Challenger" Expedition. It may, however, be useful to 
state here that the " Porcupine " Compound Ascidians include : — 

Distaplia rosea, Delia Valle. 

One colony from Tangier Bay ; 35 fathoms. 

Aplidium falkuc, Johnston. 

Two small colonies from Loch Foyle ; 10 fathoms. 

Leptoclinum, sp. 

One colony from Station 12 ("Lightning," 1868, Faeroe channel) ; 530 
fathoms. 

Leptoclinum, sp. 

Several colonies ; locality unknown. 

Leptoclinum albidum. 

Several colonies from Tangier Bay ; 35 fathoms. 

* In the summer of 1868 H.M.S. "Lightning" explored the region of the North Atlantic lying 
between the Hebrides and the Faeroes. In 1869 H.M.S. "Porcupine " made three cruises, the first off 
the north-west and west coasts of Ireland, the second off the south and south-west of Ireland, and the 
third off the north of Scotland as far as the Faeroes. In 1 870 the " Porcupine " dredged down the 
west coasts of France and Spain and in the neighbourhood of Gibraltar Strait, and explored the African 
coast of the Mediterranean as far east as Sicily. 

VOL. XXXII. PART II. 2 N 



220 DR W. A. HERDMAN ON 

Leptoclinum, n. sp. 

One colony from Tangier Bay ; 35 fathoms. 

Didemnum, sp. 

One colony from Station 54 (Freroe channel, " cold area ") ; 363 
fathoms. 

BotnjUus, sp. 

One colony from Tangier Bay ; 35 fathoms. 

BotryUus t sp. 

One colony from Station 54 (Fseroe channel, "cold area"); 363 
fathoms. 

Some of these possess an interest, apart from their morphological pecu- 
liarities, on account of the considerable depths from which they were obtained. 



ASCIDIA SIMPLICES. 

Family Ascidiid^e. 

This family is represented in the collection by three species of Ascidia. 
The common Ciona intestinalis was apparently not dredged at any of the 
localities visited. 

Ascidia scabi'a, O. F. Midler. 

About thirty specimens of this well-known species, most of them attached 
to Lamellibranch valves, were dredged in Lough Foyle, Ireland, from a depth of 
10 fathoms, during the first cruise of the " Porcupine " in 1869. Most of them 
are small. They range from 5 mm. to 25 mm. in greatest length. The shape 
varies considerably. The small individuals are ovate and much flattened; 
the larger ones are usually irregularly orbicular, but a few are oblong, and 
resemble the typical form of Ascidia virginea. The mantle is strong, and the 
muscle bands run very irregularly. 

In some remarks upon this species published in 1880, I showed how vari- 
able the branchial sac might be in the arrangement of the stigmata. * The 
" Porcupine " specimens exhibit this irregularity, and, in addition, show in 
some places an imperfect development of the internal longitudinal bars, which 
is frequently observed in Corella parallelogramma, and which I have figured 
in Ascidia triangularis A In 1880 I described the meshes in Ascidia scabra 

* "Notes on British Tunicata," Journ. Linn. Soc. Zool, vol. xv. No. 85, p. 274. 
f Loc. cit., pi. xvi. fig. 6. 



THE " PORCUPINE " AND " LIGHTNING " TUNICATA. 221 

as being usually transversely elongated, and as containing each about twelve 
stigmata; but in some of the "Porcupine" specimens the meshes are occa- 
sionally square, and have only 6-7 stigmata. Here and there at the angles of 
the meshes very short hemispherical papillae may be found on the internal 
longitudinal bars, otherwise the " Porcupine " specimens agree with the 
description and figure in the Journal of the Linnean Society. 

The large tentacles are rather stouter than those in my former figure, # but 
the arrangement is the same. The dorsal tubercle is somewhat variable in 
this species, but is always very simple. Two of the " Porcupine " specimens 
have it intermediate in shape between those figured by myself in 1880 1 and 
by JulinJ in 1881. 

In several of the specimens large masses of ova are present in the peri- 
branchial chamber. 

Ascidia plebeia, Alder, var. nov. {X) (Plate XXXV. figs. 1-3). 

External Appearance. — The body is irregularly ovate or pyriform, greatly 
compressed laterally, and attached by the posterior half, or more, of the left 
side. The anterior end is narrow and produced, the posterior considerably 
wider. The dorsal and ventral edges are irregular, but nearly equally curved; 
both sides are flattened. The branchial aperture is terminal and prominent; 
the lobes are well marked. The atrial aperture is from one-third to half way 
down the dorsal edge, prominent, projects laterally, and has well-marked 
lobes. 

The surface is somewhat irregular, but not rough. There are adhering sand 
and shell fragments at the posterior end and over part of the left side. 

The colour is yellowish- grey. 

Length of the body, 42 cm.; breadth, 1*9 cm. 

The test is moderately thick and strong, of a firm gelatinous consistency, 
translucent, smooth, and glistening on the inner surface, and richly supplied 
with blood-vessels. The left side and posterior end are thickened and made 
stiff by the presence of many imbedded sand grains and fragments of shells. 

The mantle is moderately strong. The musculature is well developed on 
the right side and the anterior end of the left, but is very slight over' the 
visceral part of the body. The sphincters are fairly strong. 

The branchial sac is slightly plicated longitudinally. The transverse 
vessels are all of the same size. The internal longitudinal bars are strong, and 
bear large curved and sometimes forked papillae at the angles of the meshes, and 
smaller simple ones between. The meshes are slightly elongated vertically, and 

* Loe. cit., pi. xvii. fig. 2. f Loc. tit., pi. xvii. fig. 1. 

\ " Recherches sur l'organisatioii des Ascidies Simples, &c," Archives de Biologie, t. ii. fasc. 1, 
pi. iv. fig. 2. 



222 DR W. A. HERDMAN ON 

contain each four to six stigmata. The horizontal membranes are slight ; there 
are none between the smaller papillae. 

The dorsal lamina is slightly ribbed transversely, and has small denticula- 
tions on the free margin. 

The tentacles are numerous, and so closely placed that their bases touch. 
There are 30 or 32 large, with about the same number of intermediate smaller 
ones. 

The dorsal tubercle is small and simple, ovate in outline, and with the 
narrower end anterior. The aperture is anterior, with the right horn rather 
longer than the left, but neither of them curved. No peritubereular area is 
present. 

Locality. — Two specimens, one large and one small, were obtained, during 
the second cruise of the " Porcupine," at Station 33, 20th July 1869, lat. 50° 
38' N., long. 9° 27' W.; depth, 75 fathoms; bot. temp., 9°*8 C. 

These specimens are exceedingly like the common Ascidia plebeia, Alder, but 
differ from it in some details. They have no trace of the greenish tinge so 
characteristic of Ascidia plebeia even after preservation in alcohol, and the test 
is firmer and stiffer. The general shape, however, and the positions of the aper- 
tures (see PI. XXXV. fig. 1) recall the characters of Ascidia plebeia. The 
measurements in the above description are those of the larger specimen ; 
the smaller one is 2*6 cm. in length and 14 cm. in breadth. In the smaller 
specimen the atrial aperture is not distant from the branchial, and is turned 
forwards. 

The body, when the test is removed, is long and narrow, and the branchial 
sac extends slightly beyond the viscera posteriorly (see PI. XXXV. fig. 2). The 
stomach is large and the intestine rather wide. It is covered with renal vesicles 
and the reproductive creca. The ovary forms thick swollen masses, and the 
spermary small dendritic tubules scattered chiefly over the anterior part of the 
intestine. The oviduct and the vas deferens are both greatly distended in 
the larger specimen, and form conspicuous curved tubes on the left side of 
the body (see PI. XXXV. fig. 2). Large quantities of ova were found in 
the peribranchial chamber. 

The branchial sac resembles that of Ascidia plebeia in every particular.* 
The primary papilla? are large (PI. XXXV. fig. 3), and in some cases bear 
pinnaB or small tubercles on the sides. Smaller transverse vessels connecting 
the intermediate or secondary papilla? appear never to be present. 

The tentacles are numerous and closely placed, more closely than I have 
found before in Ascidia plebeia, and I can only distinguish two sizes, with an 
occasional very much smaller one here and there. The dorsal lamina is very 
slightly ridged and denticulated. The prebranchial zone is papillated all over, 

* Compare description in Journ. Linn. Soc. ZooL, vol. xv. No. 85, p. 288. 



THE "PORCUPINE" AND "LIGHTNING" TITNICATA. 223 

and rather wide. There is no peritnbercular area, and the dorsal tubercle is 
small and simple, just as in Ascidia plebeia. It only occupies about one-fourth 
of the breadth of the prebranchial zone. 

After taking all the characters into consideration, I am inclined to refer the 
specimens to Ascidia plebeia, Alder, of which they may be considered as a 
variety until more is known about the range of variation in the species. 

Ascidia, sp. 

A torn test of a single individual of the genus Ascidia was found adhering 
to some fragments of Annelide tubes dredged at Station 45, lat. 35° 36', long. 
2° 29'; "Porcupine" 1870; depth, 207 fathoms; bot. temp., 12°-4C. 

As the test only is present, it is, of course, impossible to identify the 
species, but there can be no doubt as to the genus. I consider it worthy of 
record simply on account of the depth from which it was obtained. 

Family Cynthiid^e. 

No members of the sub-families Cynthin.e and Boltenin^e are in the collec- 
tion, but the Styelin^e are represented by the common Styela grossidaria, van 
Beneden, and four species of Polycarpa, three of which appear to be unde- 
scribed. One of these is from the Mediterranean, one from the Fseroe channel, 
and the other from the North Atlantic S.W. of Ireland, and from outside the 
Strait of Gibraltar, in rather deep water. 

Styela grossidaria, van Beneden. 

A large number of small individuals of this species were found attached to 
specimens of Polycarpa pomaria, dredged near Belfast on 4th August 1869, at a 
depth of 70 fathoms. 

They vary from 2 mm. to 3 mm. in greatest length. Although they are 
so small, all of those I have examined are sexually mature and contain ripe 
ova, and in some cases tailed larvae, in the peribranchial cavity. 

Also half a dozen small specimens of this species were found on a fragment 
of shell from Station 54, lat. 59° 56' N., long. 6° 27' W., during the third cruise 
of the "Porcupine" in 1869; depth, 363 fathoms; bot. temp.-0 o, 3 C. 

They are of the blister-like form, flattened antero-posteriorly, and with 
expanded margins. So far as I am aware, this is the greatest depth at which 
Styela grossularia has been obtained. It is usually regarded as a shallow water 
species, and in some localities extends up between tide marks further than 
any other species of Tunicate. 

There are also in the collection one large and six small specimens, labelled 
" ' Lightning,' off Valentia." 



224 DR W. A. HEKDMAN ON 

Polycarpa pusilla, n. sp. (Plate XXXV. figs. 4-6). 

External Appearance. — The body is spherical, ellipsoidal, ovate, or pyriform, 
is not compressed, and is unattached. The anterior end is narrower if not the 
same as the posterior, which is wide and rounded. When the shape is ellipsoidal, 
the long axis is dorso-ventral. The apertures are not distant, on the anterior 
end; in some cases prominent, in others sessile and inconspicuous; no lobes are 
visible. 

The surface is even, but completely covered by an incrusting layer of fine 
sand. Hair-like processes are present on the posterior half or so of the body, 
and bear sand grains. 

The colour is light brown. 

Length of body (in an average sized specimen), 5 mm.; breadth, 6 mm.; 
thickness, 4 mm. 

The test is moderately thick and tough, completely concealed externally by 
the sand, and smooth internally, it is continued posteriorly into the hair-like 
processes bearing sand grains. 

The mantle is rather strong. The muscle bands are numerous, though fine, 
and form a close network. Most of them compose a strong longitudinal layer 
internally, and a weaker circular layer externally. The sphincters are well 
developed. 

The branchial sac has four folds upon each side. The internal longitudinal 
bars are very broad, ribbon-like membranes: there are four or five on each fold, 
and one or two in the interspace. The meshes are rather large and square, and 
contain each five or six stigmata. In the mature sac the stigmata are long 
and narrow, and each mesh is divided transversely by a narrow horizontal 
membrane. 

The tentacles are of two sizes, with occasional smaller ones between. There 
are usually upwards of fifty altogether in the circle. 

The dorsal lamina is a narrow membrane with slight transverse ribs, which 
begin a short way from the anterior end. The edge is thickened, but has no 
denticulations. 

The dorsal tubercle is simple, and ovate in outline; the aperture is directed 
anteriorly and to the left. The horns are not coiled, but almost touch ; the long 
axis is vertical. 

Locality. — Thirty-five specimens of this species were obtained 40 miles off 
Valentia, at a depth of 110 fathoms in the North Atlantic ; and one specimen 
was obtained at Station 31, " Porcupine " 1870, lat. 35° 56' N., long. 7° 6' W., 
at a depth of 477 fathoms; bot. temp., 10 o, 3C. 

This is a curious little species, in external appearance bearing considerable 
resemblance to Polycarpa pilella, a species discovered during the "Challenger" 
Expedition at Bahia, in shallow water. The present species is usually spherical, 



THE " PORCUPINE " AND " LIGHTNING " TUNICATA. 225 

and most of the specimens look like little rough bullets covered with sand (see 
Plate XXXV. fig. 4, e. and f.). They feel quite hard, the test being rather firm. 
The specimens collected vary from 2 mm. to 9 mm. in greatest diameter. 
Most of them are small. In the majority, the apertures are not visible 
externally, and it is impossible to distinguish the ends and sides without dissec- 
tion. Ina few, however (see Plate XXXV. fig. 4, a and b.), the apertures are pro- 
minent, terminating short conical projections from the anterior end of the body. 
No lobes are visible, but when the test is removed the apertures are seen to be 
distinctly cross- slit. 

The mantle does not adhere to the test, and consequently the body can 
be readily shelled out. The musculature is well developed all over, and consists 
of two distinct layers, the internal longitudinal, starting anteriorly in bundles 
of fibres radiating from the apertures, and the external circular. Besides these, 
there are also a few oblique and irregularly running bundles. 

The branchial sac appears variable. In small (young) specimens (see 
Plate XXXV. fig. 6), the stigmata are short and rounded, and the transverse 
vessels very wide; while in the larger specimen examined, the stigmata are 
long (see Plate XXXV. fig. 5) and closely placed, and the transverse vessels all 
very narrow. The internal longitudinal bars are wide and ribbon-like. In the 
part of the sac of the large specimen examined (see Plate XXXV. fig. 5) there 
were five bars on each of two folds next the endostyle, and only a single bar in 
the interspace, while the two rows of meshes formed by this bar with the adjacent 
folds had from five to six stigmata in each mesh. The series next to the endo- 
style was wider, each mesh containing nine or ten stigmata. In the young speci- 
men examined and figured (PI. XXXV. fig. 6) the first or dorsal fold (br. f. I.) 
has seven bars, and is separated by a single row of meshes from the dorsal 
lamina, and by four rows of meshes from the second fold — hence this interspace 
has three bars. The second fold {br. f. II) has three bars, and is separated 
from the third by three rows of meshes, hence this, the second interspace, has 
two bars only. The third fold (br. f. III.) has five bars, and is separated 
from the fourth by three rows of meshes, hence this third interspace has also 
two bars. The fourth fold (br. f. IV.) has also five bars, and is separated from 
the endostyle by two rows of stigmata, or an interspace with one bar. The 
stigmata in this sac are all short and rounded, and placed far apart. There 
are usually three or four in a mesh. 

The tentacles (Plate XXXV. fig. 6) are rather irregular. Three sizes are pre- 
sent, but members of the third order are often absent, as seen near the endostyle 
at the left hand end of the figure. The polycarps are fairly numerous. Some 
are male, others female, and others hermaphrodite. The endocarps are rare. 
The stomach is globular, and deeply sulcated. 



226 DR W. A. HERDMAN ON 

Poly cm-pa curta, n. sp. (PI. XXXVI. figs. 7-11). 

External Appearance. — The body is ovate, ellipsoidal, or elongated trans- 
versely; not compressed laterally, and unattached. The anterior end is wide 
and convex, the posterior is usually still wider, and flat or irregular ; the dorsal 
and ventral edges are short and similar. The apertures are rather far apart, 
being placed at the opposite extremities of the anterior end. They are equally 
anterior, and are sessile and inconspicuous. There are no apparent lobes. 

The surface is smooth, and fairly regular, but is slightly incrusted with 
small sand grains. 

The colour varies from yellowish-grey to light brown. 

Greatest length of the body, dorso-ventrally (in an average specimen), 9 
mm. ; breadth (antero-posteriorly), 7 mm. ; thickness, (laterally), 5 mm. 

The test is thin, but very tough and leathery. It is quite opaque. The 
outer surface is slightly sandy, and the posterior end has a few hair-like pro- 
longations, to which sand grains are attached. 

The mantle does not adhere to the test. The apertures are slightly cross- 
slit, and the sphincters surrounding them are strong. The musculature else- 
where on the mantle is well developed, the muscle bands forming a close net- 
work not clearly divided into longitudinal and circular layers. 

The branchial sac has four well-marked folds on each side. The most dor- 
sally placed is larger than the others, and has about twelve internal longitudinal 
bars. Th e rest of the folds have about six bars each, and there are two bars 
in each interspace. All the internal longitudinal bars are flat, ribbon-like 
membranes of considerable width. The transverse vessels are all of the same 
size. The meshes are about square, and contain each four or five stigmata. 

The dorsal lamina is a narrow membrane, with no ribs and no denticulations. 

The tentacles are not very numerous. There are eighteen or twenty large 
tentacles, and the same number of smaller intermediate ones. 

The dorsal tubercle is simple. It is fusiform in outline, with the long axis 
vertical. There is an irregular slit down the middle, but there is no curvature, 
hence no horns are present. 

Locality. — Sixteen specimens of this species were dredged at Station 12; 
" Lightning," 1868; lat. 59° 36' K, long. 7° 20' W.; depth, 530 fathoms ; bot. 
temp., 6° -4 C. 

This species is allied to Polycarpa pusilla, but differs both in external appear- 
ance and in internal structure. It is not so much incrusted with sand, and the 
shape, though variable in both species, is here more decidedly elongated dorso- 
ventrally (Plate XXXVI. figs. 7 and 8), the result being the apertures come to be 
placed far apart at the opposite extremities of the wide anterior end (see Plate 
X XXVI. fig. 7). The greatest length is always dorso-ventrally, and this ranges in 
the specimens collected from 5 mm. to 13 mm. 



THE "PORCUPINE" AND "LIGHTNING" TTJNICATA. 227 

The branchial sac has the folds (Plate XXXVI. fig. 9) better developed than 
in Poly car-pa pusilla. In one sac examined the arrangement, starting from the 
dorsal lamina along the right hand side, was — one row of wide meshes con- 
taining 8 to 10 stigmata, then the 1st fold with 12 bars, then the 1st interspace 
with 2 bars, then the 2nd fold with 7 bars, then the 2nd interspace with 2 bars, 
then the 3rd fold with 7 bars, then the 3rd interspace with 3 bars, then the 4th 
fold with 6 bars, and then a row of wide meshes separating the ventral fold from 
the endostyle. Figure 10 on Plate XXXVI. shows the narrow dorsal lamina 
and the wide row of meshes separating it from the commencement of the first 
fold on the left side of the sac. A large number of fine muscle fibres are 
present in the branchial sac, chiefly in the transverse vessels. 

The peritubercular area (Plate XXXVI. fig. 2) is large and triangular in 
shape. It is almost perfectly symmetrical. The tubercle is very different 
from that of Polycarpa pusilla. It is comparatively simple, since the slit, 
though irregular in shape, is not curved to form horns or spirals (see Plate 
XXXVI. fig. 11, d. t.). The polycarps are irregularly rounded ; they are herma- 
phrodite. Endocarps are not numerous. 

Polycarpa pomaria, Savigny. 

Twelve moderately large specimens of this common species were dredged 
on August 4, 1869, near Belfast, at a depth of 70 fathoms. The largest indi- 
vidual measures 3 cm. in length and 2 cm. in breadth. 

Three or four of the specimens differ somewhat in appearance from the 
rest ; their tests are thinner and smoother, but otherwise they appear to be 
exactly the same. 

A single individual of this species was also obtained in 1870 in Tangier Bay 
from a depth of 35 fathoms. The test is stiff, giving a solid appearance and 
feel to the specimen, and the exterior is somewhat incrusted with sand. The 
difference in external appearance between this individual and those with smooth 
thin tests from near Belfast is very considerable, but the species is a variable 
one, and intermediate forms are common. 

Polycarpa formosa, n. sp. (Plate XXXVI. figs. 1-6). 

External Appearance. — The body is elongated antero-posteriorly, and varies 
from pyriform to oblong in shape. There is almost no lateral compression, and 
attachment is by the posterior extremity. The anterior end is moderately 
wide, but narrower than the middle of the body. The posterior end is narrower 
than the anterior. The widest region is usually a little behind the middle of 
the body. The apertures are both anterior, and not distant. They form slight 
papilla?, and are each distinctly four-lobed. 

The surface is even, but considerably incrusted with sand grains, especially 

VOL. XXXII. PART II. 2 O 



228 



DE W. A. HERDMAN ON 



at the posterior end, where there are also root-like prolongations of the test, 
to which sand is attached. 

The colour is light grey where the test is exposed; reddish-brown from 
the sand elsewhere. 

Length of the body (average specimen), 1*5 cm.; breadth, "7 cm.; length 
of the root-like appendages, 1 cm. to 2 cm. 

The test is thin, but moderately tough. It is translucent where free from 
sand. The posterior end from which the sandy prolongations spring is some- 
what thickened. 

The mantle is rather slight. The muscle bands are feeble, and not very 
numerous ; they form an open irregular network. 

The branchial sac has four folds upon each side. Each fold is formed by 
the aggregation of from six to twelve internal longitudinal bars. There are 
two to four bars in each interspace. The transverse vessels are of two sizes, 
alternating regularly. The meshes are much elongated vertically, and contain 
about three or four stigmata each. The stigmata are long and narrow, and the 
meshes are divided transversely by a narrow horizontal membrane. 

The dorsal lamina is rather wide, and has irregular and partial transverse 
ribs ; the margin is smooth. 

The tentacles are numerous, and closely placed. They are large, and all of 
much the same size. 

The dorsal tubercle is a simple, slightly-curved band, with the extremities 
directed posteriorly. 

Locality. — Six specimens were dredged in Tangier Bay, on the 5th August 
1870, from a depth of 35 fathoms. 

There is a characteristic appearance about the specimens of this species, 
although they all differ somewhat in shape (see Plate XXXVI. figs. 1-3). In 
all, the apertures are closely placed at the anterior end, the body is elongated 
antero-posteriorly, and the posterior end is prolonged into a mass of branched 
projections covered with sand. The dimensions of the six specimens are as 
follows : — 





A. 


B. 


C. 


D. 


E. 


F. 


Length of body alone, 


2-0 cm. 


1*5 cm. 


l - 5 cm. 


T6 cm. 


1-0 cm. 


1*4 cm. 


Length of posterior projections, 


11 cm. 


0-7 cm. 


2-2 cm. 


1-0 cm. 


l - 4cm. 


2 - 5 cm. 


Breadth of body, 


11 cm. 


0-9 cm. 


07 cm. 


07 cm. 


- 6 cm. 


05 cm. 



The folds in the branchial sac (PI. XXXVI. fig. 5), although they have a con- 



THE " POPCUPINE " AND " LIGHTNING " TUNICATA. 229 

siderable number of internal longitudinal bars, do not project much into the 
cavity. The sac, as a whole, is very similar in structure to those of Styela 
oblonga, S.fia/ca and S. glans* 

The dorsal tubercle is very simple, the prebranchial zone is narrow (Plate 
XXXVI. fig. 6), and the peritubercular area small, and not occupied by the 
tubercle. The tentacles are of considerable size, and have large bases. 

Polycarps are not very numerous. They are scattered over the inner surface 
of the mantle (Plate XXXVI. fig. 4, g.). They are unisexual. The male poly- 
carps are deeply cleft into lobes. 

The alimentary canal lies on the dorsal part of the left side of the body. 
The stomach is pyriform, and is strongly ribbed externally ; the intestinal loop 
is moderately open, and the rectum is long and narrow (see Plate XXXVI. 
fig. 4, v.). 

Family MolgulidyE. 

This family is represented in the collection by two species of Molgula and 
the common Eugyra glutinans. 

Molgula, sp. 

A single small specimen of a Molgula, slightly torn, was found adhering to 
one of the specimens of Polycarpa pomaria from near Belfast ; 70 fathoms. 

The shape is nearly globular; 8 mm. in diameter, and slightly compressed 
laterally. Short hair-like processes project all over, and have a few grains of 
sand and other foreign bodies attached to them, but there is no incrusting coat. 
The test is moderately thin, soft, and nearly transparent. The colour is light 
yellowish-grey. Possibly this may be Molgula nana, Kupffer. 

Molgula ampulloides, van Beneden. 

One specimen of this rather widely-diffused species was dredged in Lough 
Foyle, during the first cruise of the " Porcupine " in 1869, from a depth of 10 
fathoms. It measures 17 cm. in length, and 1*4 cm. in greatest breadth. 

Eugyra glutinans, Moller (Plate XXXVI. figs. 12-14). 

Eighteen specimens of this common and apparently gregarious species were 
dredged in Donegal Bay, Ireland. 

None of the specimens are large. They range from 4 mm. to 12 mm. in 
greatest diameter. The incrusting sand is very fine and comes off readily, the 
result being that most of the specimens have very little left, and in some the 
delicate test is almost completely exposed. 

* See Eeport upon the Tunicata dredged during the voyage of H.M.S. " Challenger," Part I. 
Plate XX. figs. 4, 8, and 11. 



230 DR W. A. HERDMAN ON 

In the branchial sacs of several of these specimens, the vessels forming the 
apices of the spiral infundibula are considerably swollen, attaining as much as 
twice their normal calibre (Plate XXXVI. figs. 12 and 13); and the epithelium 
on the edges of the corresponding stigmata is greatly thickened (see Plate 
XXXVI. fig. 14). 

Postscript, May 30, 1884. — Since the above paper was written and the 
plates finished, I have received, through the kindness of Dr P. Herbert 
Carpenter, three specimens of an interesting and apparently unclescribed 
Molgulid, which was dredged from a depth of 440 fathoms in the Faeroe 
channel during the third cruise of the " Porcupine" in 1869. This species will 
be described and figured in the Report on the " Challenger " Tunicata, Part II. 



EXPLANATION OF THE PLATES. 
The following system of lettering has been adhered to in all the figures : — 

at. Atrial aperture. 
br. Branchial aperture. 
br. f. Fold in the branchial sac. 
d. I. Dorsal lamina. 
d. t. Dorsal tubercle. 
en. Endostyle. 
(j. Genital organ. 
h. m. Horizontal membrane of the branchial sac. 
i. I. Internal longitudinal bar of the branchial sac. 
m. The mantle. 
p.,p'. Papillae of the branchial sac. 
p. p. The peripharyngeal bands. 
r. The rectum. 

sg. The stigmata of the branchial sac. 
st. The stomach. 
tn., tn. The tentacles. 
tr., tr'., tr". The transverse vessels of the branchial sac. 
z. The prebranchial zone. 

PLATE XXXV. 

Figs. 1-3. Ascidia plebeia, Alder, var. nov. 
Figs. 4-6, Polycarpa pusilla, n. sp. 

Fig. 1. Ascidia plebeia, var., seen from right side ; natural size. 

Fig. 2. Ascidia plebeia, var., the test removed, body seen from the left side ; natural size, 



THE " PORCUPINE " AND " LIGHTNING" TUNICATA. 231 

Fig. 3. Small part of the branchial sac of Ascidia plebeia, var., seen from the inside ; magnified 
50 diameters. 

Fig. 4. a. — f. Six specimens of Polycarpa pusilla, n. sp. ; natural size. 

Fig. 5. Small part of the branchial sac of Polycarpa pusilla, seen from the inside ; magnified 50 
diameters. 

Fig. 6. Eight half of the anterior part of the branchial sac, showing also the tentacles, the 
endostyle, the dorsal tubercle, the prebranchial zone, &c; magnified 50 dia- 
meters. 

PLATE XXXVI. 

Figs. 1-6. Polycarpa formosa, n. sp. 
Figs. 7-11. Polycarpa curta, n. sp. 
Figs. 12-14. Eugyra glutinans, Moller. 

Fig. 1. Polycarpa formosa, from the right side ; natural size. 

Fig. 2. Another specimen of the same species. 

Fig. 3. Group of one small and two large specimens of the same species ; natural size. 

Fig. 4. Specimen of Polycarpa formosa, dissected from the left side to show the alimentary- 
canal, &c; slightly enlarged. 

Fig. 5. Small part of the branchial sac of Polycarpa formosa, seen from the inside ; magnified 
50 diameters. 

Fig. 6. Dorsal tubercle, &c, of Polycarpa formosa ; magnified 50 diameters. 

Fig. 7. Specimen of Polycarpa curia; natural size. The arrows indicate the branchial 
(inhalent) and atrial (exhalent) apertures. 

Fig. 8. Two other specimens of the same species. 

Fig. 9. Small part of the branchial sac of Polycarpa, curta, seen from the inside ; magnified 50 
diameters. 

Fig. 10. Small part of the dorsal lamina and branchial sac of Polycarpa curta, from inside ; 
magnified 50 diameters. 

Fig. 11. Dorsal tubercle and peritubercular area of Polycarpa curta ; magnified 50 diameters. 

Fig. 12. Centre of a spiral from branchial sac of Eugyra glutinans ; magnified 50 diameters. 

Fig. 13. Centre of another spiral from the branchial sac of Eugyra, glutinans ; magnified 50 
diameters. 

Fig. 14. Another similar spiral from Eugyra glutinans ; magnified 300 diameters. 



VOL. XXXII. PART II. 2 P 



Roy. Soc. Edm r Vol XXXI I. 



- 



■ 










: 



f'7f/. -f<. 



Plate JXXXV 



b'~ 



Fy. 2. 





w. J. 



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s- 



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in A 









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v^ . 



/ 



ir. r. 



Figs. /-J. ASCIDIA PLEBEIA. Alder, i/an nos 
F/gs. 4-6. POLYCARPA P.USILLA, n.sp. 



T.Dobb*LC° Uth.? Lpool. 



ay, Soc. EdinT Vol XXXI I. 



Fig. 3 




Fig 6 




Fig . 




Fig. 12. 



Fig. 13 




Fig hi: 



"ft 



Fig. 11 



Plate 3XXVJ 



Fvg.2. 




Fig. 1. 



Fig. 5 



hv./:. 




V 



Fig. 9. 



>^ 



■PP- Fig W. 




n 



6. POLYCARPA FORMOSA 
Figs, 7-//. POLYCARPA CURTA n.sp. 
Figs, /F/4-, EUGYRA GLUTINANS, Mailer. 



Ir.f- 




T.JJobb &. C Lith» JJpool. 



( 233 ) 



XIV. — Note on Sir David Breivster's Line Y, in the infra- Red of the Solar 
Spectrum. By C. Piazzi Smyth, Astronomer Eoyal for Scotland. (Plate 
XXXVII). 

(Read 17th December 1883.) 

Of all known examples in physical science, of simplifying, and at the same 
time " precisionising " some of its fundamental data, which might otherwise 
fall to be entangled in high numbers, none has been happier than Fraunhofer's 
application of the letters of the alphabet to certain chief lines in the solar 
spectrum. Happy both in its conception by the inventor, and its universal 
acceptance since then by the world. Whence it comes to pass now, that in every 
country, whoever observes the solar spectrum at all, with whatever instrument, 
large or small, diffracting or refracting, and whether he holds to the undulatory, 
or any other theory of light, and catalogues spectral lines either in Wave-lengths 
or Wave-numbers, or merely in terms of the brass scale screwed to his instru- 
ment by a maker, — yet whenever he- speaks of the line A, or B, or C, or 
any other so named by Fraunhofer, he singles out thereby from among 
thousands, exactly the same identical line which any and every other spectro- 
scopist alludes to under the same simple letter. 

Hardly less happy was the extension of the system made by our great 
specialist in optical physics, Sir David Brewster, when, having discovered 
several lines in the infra-red of the solar spectrum, beyond or before Fraun- 
hofer's commencing line " great A " — he named them with the later letters of 
the alphabet, whose stock of symbols had not been more than half used up 
by Fraunhofer in reaching toward the further violet end of the spectrum. 
Hence, without disturbing any one of Fraunhofer's lettered lines from red 
through green, to blue and violet, Brewster called his new line next beyond, 
or before great A in the "infra red," by the letter Z; the next before and 
outside that, Y ; and the next before that again, X. 

In so far, Brewster's proceeding was quite as happy as Fraunhofer's ; and 
if his assigned letters have been lately misused or omitted in certain high 
quarters, that is not his fault, and perhaps not intentional on the part of those 
who have done so, but has arisen firstly from the difficulty that many observers 
have in seeing his lines in the ultra-red, on account of their exceeding faint- 
ness; and secondly, from some of them being Solar, and others Telluric, to a degree 
that even he himself had not fully anticipated. It would seem, therefore, to be 
high time, in Brewster's own Society and Country, to come to a clearer under- 
standing on the facts of his nomenclature, touching at least those three chief 

VOL. XXXII. PART II. 2 Q 



•2:54 C. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER'S 

lines X, Y, Z ; and the case is all the more claimant just now, seeing that a 
very grand chemical identification has just been made out in France for one of 
them ; but one, unhappily of late called after one letter by some persons, and 
another letter by others, a fruitful source of future trouble unless corrected 
speedily. I propose, therefore, to inquire here, by help of a few recent obser- 
vations, and reference to many old ones, which is the right letter to employ for 
each of those three lines. 

Sir David Brewster's activities in Solar- spectrum observation were in full 
force at his favourite Border seat of Allerly, in 1833, as evidenced by three 
spectroscopic papers in our volume of Transactions for that year ; but the fullest 
and most authoritative publication on his new lines in the infra-red is that con- 
tained in his joint paper with Dr Gladstone in the Philosophical Transactions 
of the Royal Society, London, in 1860. 

Of the longest spectrum- view contained in a plate accompanying that paper, 
I submit a portion copied by myself, as Strip No. 1 of my own plate now pre- 
sented, with very little alteration, except slightly expanding it to suit my scale ; 
and freely crossing and recrossing the lines representing both shade and the 
inevitable darkness at and about the very origin of spectrum light, which, 
beginning on the left-hand side of the picture, rapidly increases in intensity 
towards the right — Fraunhofer lines and bands therein always excepted. 

As an observer, I like Sir David's drawing much, for its truthful representa- 
tion of the real and necessary degree of darkness, in midst of, or antagonistically 
to, which the new lines had to be detected; a feature of Nature, this darkness 
at either end of the spectrum, so rarely introduced in modern spectrum draw- 
ings. And though the shade bands are rather too sharply defined on either 
edge, I recognise, in spite of the depreciatory comments of M. Kirchoef, that 
it is exceedingly like what appears at that end of the spectrum, when a spec- 
troscope is under-prismed and over-telescoped. So too it must most eminently 
have been in Sir David's case, when he seems to have employed but one simple 
prism of not very heavy glass, and no less than a 5-foot achromatic telescope 
to look into it. But then it was Brewster's eye that looked ; so no wonder 
that he saw with it more than any of his predecessors, and most of his suc- 
cessors as well. 

" The light less refrangible than A," say the conjoint authors at their page 
1.30, " is red, but extremely faint, so faint indeed, that few observers of the spec- 
trum have perhaps ever seen it; and the only drawing hitherto published of lines 
in it appears to be in a map of the solar spectrum by M. Matthiesen of 
Altona. He represents a few lines which, on comparison with fig. 1, may be 
identified as the band anterior to Y, Y itself, and the band Y 1 . In order to map 
the lines and bands in this portion of the prismatic image, Sir David Brewstek 
was obliged to take extraordinary precautions. The telescope was lined with 



LINE Y, IN THE INFRA-PLED OF THE SOLAR SPECTRUM. 235 

black velvet, in order to exclude any reflected light ; a low power was em- 
ployed; the slit was made about the eighth, or tenth, of an inch wide,* and 
the eye of the observer was washed with water to cleanse the fluid that lubri- 
cates the cornea. The most prominent line in this space is that marked Y." 

That last remark is quite to our purpose, and I trust the drawing-strip, 
No. 1, of the Plate now given, illustrates it perfectly, remembering that " great 
A" and "little a" are introduced merely to give milestone references to known 
parts of the spectrum, and a measuring test universally understood for scale. 

Strip No. 2 represents some rude efforts of mine in 1871, with very unequal 
apparatus, to see something of this rare region of the ultra-red. The drawing 
is slightly altered from that in Vol. XIII. of the Edinburgh Astronomical Obser- 
vations, inasmuch as the mere general appearances of many close, thin lines 
unmeasured, and of shading, improperly represented there by vertical lines, are 
here crossed diagonally and horizontally in such a manner that they cannot be 
understood to imply true, resolved spectral lines, or anything but shade only, 
symbolically expressed. And the chief result is thereby plainer than ever, viz., 
that the Y line was better seen in a high summer, than a low winter, sun ; a 
feature indicating it to be of Solar origin, and not of Earth's atmosphere, or 
" Telluric " intervention. 

Strip No. 3 gives the two views of high and low sun, contained in the Royal 
Society's Himalaya spectrum, in their Philosophical Transactions for 1875. 
This drawing is on a smaller scale than their's ; and their questionable shadings 
with vertical lines have been changed by me into diagonal lines ; but otherwise 
it represents in exactly the same manner their very surprising negation of the 
visibility of Y in a high sun, but its abundant visibility, and that of Brewster's 
Z also, in a low sun. 

Strip No. 4 represents on a reduced scale my own observations (from 
Vol. XIV. of Ed. Ast. Obs.) made in Portugal in 1877, with a far more powerful 
spectroscope than I had ever possessed before, and which I had had constructed 
specially to look into this particular question of the visibility, or non-visibility, 
of the Y line in a very high, indeed almost Zenithal, sun. The result, as will 
be seen in the drawing, was to confirm the previous Edinburgh observation, and 
to show that Y was, with the sun near the zenith, most notably visible ; Brew- 
ster's X appearing next in strength ; but Z only in the faintest manner possible, 
if at all. 

Strip No. 5 is a very reduced copy of part of a magnificent work derived 
from photography by Captain Abney and Colonel Festing, forming the 
Bakerian Lecture at the Royal Society for 1880. 

* The distance of this slit is unfortunately not stated. It may have been at the other end of a 
long room, and was apparently unfurnished with any kind of collimator lens, in the improved manner 
introduced by Professor Swan. 



236 C. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER'S 

By dint of Captain Abney's really wonderful processes of changing the colour 
of silver for transmitted light, he was enabled to photograph not only all that 
part of the infra-red end of the solar spectrum discovered with so much pain 
and labour by Brewster, but to procure records of other lines, some of them 
very grand ones too, extending nearly three times as far away, and into what 
is, to the human eye, absolute, unmitigated darkness. There is, therefore, not 
the slightest intention here to compete with him in spectral range ; and I have 
purposely left his spectrum strip bright and of full height up to the extreme left 
hand end of my paper, to indicate that his view extends very much further still 
in that same direction. The only point of difference in fact which I have with 
him and his distinguished fellow-labourer, or the Central Metropolitan Society 
which publishes their work, is, — that the very strong line, which from its place 
in the spectrum can be no other whatever than Y, he calls Z ; and the letter Y 
he gives no place to. 

Apparently Captain Abney and Colonel Festing had not seen the real Z line 
at all ; and with little doubt because they worked in a too high Sun for it, 
though excellent for their other, and chief, objects. For Strip 6 shows the result 
of three observations which I had the fortune to make during an unusually long, 
bright sun-shiny afternoon on the 30th of May last at the house No. 15 Eoyal 
Terrace, Edinburgh. The apparatus was moderate in power ; there was 
no attempt to resolve bands into their very thin component lines ; but only to 
note the main features of Y and Z, " Great A" being given in as a necessary 
mile-stone. 

At 5 h 50 m p.m. then, of distinct lines, Y alone was visible outside Great A. 

At 6 h 40'" p.m., with a lower Sun, besides Y, there was a suspicion of Z. 
But 

At 8 h m p.m., with a very much lower Sun, there, besides Y nearly as before, 
stood out Z as quite a strong line, accompanied too with bands, and proving 
itself to be Telluric without a doubt. 

Finally, Strip 7 represents what the ancient Greeks might have called the 
apotheosis of line Y, in its glorious identification at last by M. Henri Becquerel, 
with a bright emission line of the same Solar Sodium (Na), which produces that 
grand turning key to all the modern developments of Spectrum analysis, viz., 
the Solar lines D 1 and D 2 . 

The fullest account of this final confirmation of the Solar character of Y 
that I have yet seen is that contained in the Comjries Rendus for July 9, 1883, 
pp. 71-74, by M. Henri Becquerel himself. He had been researching the 
infra-red spectrum of chemistry by his celebrated Father's method of the pheno- 
mena of Phosphorescence, and found two new distinct and widely separated 
salt lines to exist therein. He next proved the correspondence of both of them 
with'two extra strong and equally widely separated lines at the same points of 



LINE Y, IN THE INFRA-RED OF THE SOLAR SPECTRUM. 237 

the Solar spectrum. One, and the fainter of these two lines, was an immense 
distance further into visual darkness than any of the lines in my plate. It was 
even beyond Captain Abney's and Colonel Festing's furthest photographic, 
being at 23 130 Wave Number. But the other, at 31 010 W.N.— to be freely 
taken as equivalent to our 30 860 — is no less than Brewster's Y, and is 
honourably mentioned by M. Becquerel as being such. 

It is indeed so instructive, as well as encouraging, to find the line thus 
alluded to in Paris as " Brewster's Y line," three years after that letter was 
expunged in London from the Solar spectrum, that I beg to conclude with 
M. Henri Becquerel's own words thus : — 

" La vapeur de sodium, qui est principalement caracte'ris6e dans le spectre 
lumineux par la double raie D, pre'sente dans l'infra-rouge deux tres fortes raies 
caracteVistiques dont les longeurs d'onde sont 819 ( = W.N.Br. 31 010) et 1098 
( = W.N.Br. 23 130). Ces raies sont les memes lorsqu'on volatilise dans Tare, 
du sodium metallique ou clu chlorure de sodium; elles coincide avec deux fortes 
raies du spectre solaire. 

" La raie X 819 (W.N. 31 010) que Ton peut voir a l'ceil nu avec un spectro- 
scope ordinaire, coincide avec une des plus fortes raies du spectre infra-rouge 
du Soleil que Brewster avait vue, et designee par la lettre Y. 

"Dans les conditions ou Ton de'double les raies D, je n'ai pu dedoubler 
distinctement la raie Y." 

POSTSCRIPT. 

The above concluding remark of M. H. Becquerel is instructive to those 
who would desire to see for themselves this salt representative of Brewster's 
Y line ; for it shows that even in his "Arc " light, notwithstanding its necessary 
brilliance, that particular line must have been too faint for neat physical 
notation ; and, indeed, unless an arc light can be prepared as bright as, or 
possibly still brighter intrinsically than, a high summer sun, such almost must 
be the result. 

With the most powerful Bunsen gas burners, consuming any amount of 
Chloride of Sodium, the trial is quite hopeless; and even with 1-inch induction 
sparks, condensed by a half-gallon jar between platinum points, of which one 
rises through moistened salt, with the effect of making the D lines painfully 
bright, I have not succeeded in causing the same salt's Y line, or lines, to 
certainly appear. 

I have, however, in the search found three air lines much further towards 
the infra-red than any of the standard list of air lines entered in Dr Watt's 
invaluable Index of Spectra, as compiled by him from the observations of the 
greater spectroscopists. 

VOL. XXXII. PART II. 2 R 



238 C. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER'S LINE Y. 

Though not quite so far to that end of the spectrum as certain two lines of 
Rubidium, yet being much more constant and more easily procured, these new 
lines may be useful to other researchers as references for spectrum place in 
that rather barren region. I give their approximate Wave-number readings 
therefore here, and have depicted their appearance in the last or " appended " 
spectrum strip of our table, desiring to remark only, in addition, that the 
middle line of the three is triple, the distance between its first and second 
components being rather greater, and between its second and third rather less, 
than the potassium a * aml 2 pair, whose Wave-number places are 32 988 and 
33 128, respectively ; while all the three air lines appear fairly sharp, with a 
narrow slit, and under a dispersion of 12° A to H, combined with a magnifying 
power on the inspecting telescope of 15. 

Air Line 1, Rel. Intensity = 5, Wave-number place in Brit. Inch = 32 693 
r Its " a " component, Intens. = 5, W.N.P1. „ = 33 944 

Air Line 2, ) „ "b" „ „ =3, „ „ =34071 

\ ,, c ,, „ =2, ,, ,, =34 157 

Continuous spectrum begins soon after this, and goes on increasing towards the violet. 

Air Line 3, Rel. Intensity = 6, W.N.P1. in Brit. Inch. =35 404 

First Air Line in Dr Watts' Index of Spectra, Intens = 6, W.N. PI. = 38 470 

Note added on May 30, 1884. 

In the course of sundry spectroscopic experiments on vacuum tubes 
through the winter of 1883-4, and now communicated to Royal Society, 
Edinburgh, I have had abundant testimony that the first of the lines noted 
above, viz., at 32 693 Wave-number place, is an oxygen line ; a very remarkable 
one too, for though like all other "tube," or simple-spark, oxygen lines, it is 
very faint, — yet it is well-defined, and is further towards the ultra red than any 
line or band I have yet come across in any of the other gases. 

The triple line which follows I have equally proved to belong to nitrogen. 

But to what gas, air line 3, at 35 404 Wave-number place belongs, I have 
obtained no indication as yet from vacuum tubes. C. P. S. 



r. Soc. Edink. 



Plate XXXVII. 



Approximate Spectrum Drawings for the History of 
Sir David Brewster's Line Y in the Infra-Red of the 

Sola r Spectr u m. 



Scale of Wave Number in British Inch. 




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PHOTO-LITHO. BY A. RITCHIE & iON, EOIN. 



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( 239 ) 



XV. — On the Formation of Small Clear Spaces in Dusty Air. By 
Mr John Aitken. (Plate XXXVIII.) 

(Received December 27, 1883 ; read January 21, 1884.) 

The dust particles floating in our atmosphere are every day demanding 
more and more attention. As our knowledge of these unseen particles in- 
creases, our interest deepens, and I might almost say gives place to anxiety, 
when we realise the vast importance these dust particles have on life, whether 
it be those inorganic ones so small as to be beyond the powers of the 
microscope, or those larger organic ones which float unseen through our 
atmosphere, and which, though invisible, are yet the messengers of sickness 
and of death to many — messengers far more real and certain than poet or 
painter has ever conceived. 

As the great importance of these dust particles is gradually being realised, 
we are from time to time increasing our efforts to protect ourselves from these 
invisible enemies. Professor, now Sir Joseph, Lister has shown us how to 
contend successfully with those organic germs, which, falling on our wounds, 
there find a suitable resting-place, and, if not killed, germinate and grow to 
our destruction. Sanitary societies are every day being formed, one of whose 
objects is to combat these floating particles by better appliances directed 
towards the prevention of the conditions suitable for the germination, growth, 
and increase of these germs, and against their spread from infected centres, 
while other societies are directing their energies against the artificial produc- 
tion of those inorganic forms of dust which pollute our atmosphere. 

The immense importance of everything connected with dust must be my 
excuse for bringing before this Society observations on phenomena which I fear 
must appear to many as trivial and uninteresting; as the clear spaces to 
which I shall direct attention are on almost a microscopic scale, and require to 
be magnified to enable us to see them clearly. 

Professor Tyndall has made many experiments on the light-reflecting par- 
ticles floating in our atmosphere. He found these particles were destroyed by 
heat, and that by placing a flame under a brilliant beam of light, which revealed 
by illuminating the dust in the air, there was seen rising from the flame wreaths 
of darkness resembling intensely black smoke. lie then found it was not 
necessary to burn the particles to produce this stream of darkness. This was 
observed when a hot metal ball was placed under the beam of light, and per- 
mitted to remain till its temperature had fallen below that of boiling water. It 

VOL. XXXII. PART II. 2 S 



240 ME JOHN AITKEN ON THE 

was then found that, though the dark current was much enfeebled, it was still 
produced. To study this effect, Professor Tyndall stretched a platinum wire 
transversely under the beam, the two ends of the wire being connected with 
the poles of a voltaic battery, and the necessary appliances for regulating the 
strength of the current. " Beginning with a feeble current, the temperature of 
the wire was gradually augmented ; but long before it reached the heat of 
ignition a flat stream of air rose from it, which, when looked at edgeways, 
appeared darker and sharper than one of the blackest lines of Fraunhofer in 
a purified spectrum " (see fig. 5). He goes on to say — " Right and left of this 
dark vertical band the floating matter rose upwards, bounding definitely the 
non-luminous stream of air. What is the explanation ? Simply this : The hot 
wire rarefied the air in contact with it, but it did not equally lighten the float- 
ing matter. The convection current of pure air therefore passed upwards 
among the inert particles, dragging them after it right and left, but forming 
between them an impassable black partition." * 

This explanation of Professor Tyndall's has been received by most of us 
without question ; yet I think that if we try to form a mental picture of the 
process which is here supposed to go on, we shall have some difficulty in doing 
so. Professor Tyndall supposes the distribution of the floating matter is due 
to the heat, which lightens the air, but does not in the same degree lighten the 
floating dust ; the tendency, therefore, he says, is to start a current of clear air 
through the mote-filled air. No doubt the lightening of the air will slightly 
increase the tendency of the motes to fall, but the increased freedom to fall 
from this cause will be extremely slight and inappreciable, and will be entirely 
negatived and overruled by the upward movement of the hotter air, and the 
result will be simply to cause the particles to lag a little behind the air in 
their movements. 

Our confidence in Professor Tyndall's explanation was not, however, shaken 
till Lord Rayleigh, in going over Professor Tyndall's experiments and extend- 
ing them, discovered that the explanation given of the formation of the dark 
plane was not correct, and showed that it could not be due to heat lightening 
the air, and so enabling it to shake itself free from the dust motes, because he 
discovered that cooling the air produced a precisely similar result (see fig. 2). 
Lord Rayleigh introduced a cold glass rod into smoky air, and then found 
that " a dark plane extending doivnwards from the rod, clearly developed itself, 
and persisted for a long while." t He says — " This result not merely shows that 
the dark plane is not due to evaporation, but also excludes any explanation 
depending upon an augmentation in the difference of densities of fluid and 

* Proe, Roy. Inst., vol. vi. p. 3, 1870; also Essays on the Floating Matter in the Air, p. ■">. 
I o mans, Green, & Co., 1881. 

' Papei read before Royal Society, December 21, 1882; also Nature, vol. xxviii. p. 139. 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 241 

foreign matter." Lord Rayleigh also offers as a suggestion that the particles 
may be thrown out by the centrifugal force, as the mixture flows in curved 
lines round the obstacle. 

In a letter to Nature of July 26, 1883, Dr Lodge gives an account of some 
experiments he made on the dark plane and on dusty air. Dr Lodge says — 
" We are now pretty well convinced that differences of temperature have 
nothing to do with the real nature of the phenomenon ; we find that solid bodies 
have sharply defined dust-free coats or films oj uniform thickness always surround- 
ing them, and that these coats can be continually taken off them, and as con- 
tinually renewed, by any current of air." Dr Lodge also describes a number 
of interesting electrical experiments on the dust, and makes many very valuable 
suggestions, but comes to no definite conclusion. He says — " Why .the air near 
a solid is free from dust we are not prepared to say." 

From these quotations it will be seen that the whole matter is involved in 
considerable obscurity; and as the subject already had considerable attractions 
for me, I determined to undertake an investigation in this particular direction. 
My experiments were begun in summer, but it was not till November that the 
greater part of the work was done. 

I have considerable difficulty in determining how it will be best for me to 
place the result of this investigation on record. As a rule, it is best to take 
the reader over the road traversed by the investigator, as the probability is the 
difficulties of the one will be the same as those of the other, and the results 
generally unfold themselves best when treated in this way. In the present 
occasion this method is not suitable. The subject, though apparently simple 
enough, Avas found to be much more intricate and complicated than was 
expected. The result was, many a false scent was followed only to be given 
up, so that I would be taking the reader to my conclusions by a long, winding, 
and uninteresting path. It will therefore be better for me simply to describe 
the result of the investigation from my present point of view. 

Apparatus used. 

The apparatus used was all of the simplest and least expensive kind. The 
dust-box in which the experiments were made was a cigar-box, the lid of 
which was removed and a piece of glass put in its place. When in use the 
box was placed on its end, with the glass to the front. A window was cut out 
of the left side of the box, extending from close to the bottom to near the top, 
and coining close to the front of the box. The box was then painted black 
inside. Holes were cut in the back of the box, or wherever required for the 
introduction of the different pieces of apparatus, which shall be afterwards 
described. As a source of illumination, two gas jets, placed close to each 



242 MR JOHN AITKEN ON THE 

other, were used ; these jets were enclosed in a dark lantern, having an opening 
towards the dust-box. To concentrate the light, two double convex lenses were 
fitted into a short tube. This tube was loosely attached to the front of the dark 
lantern, and could be directed to, and focused on, any part in the interior of the 
dust-box. For observing the phenomena two magnifying glasses were employed 
— one a simple double convex lens, which was used for getting a general view 
of the phenomena ; the other a more powerful compound glass, strong enough 
to enable me to see and follow the movements of the individual dust particles. 

For observations on the effects of slight differences of temperature, metal 
or glass tubes in some form or other were generally used. Straight tubes closed 
at one end were found most convenient; these tubes were introduced through 
the back of the box, and the closed end projected inwards to within a short dis- 
tance of the glass front, so as to admit of observation under the strong magni- 
fying glass. The tubes were heated or cooled by means of water or steam 
introduced into them through a small tube which passed clown their interior. 
This small tube was connected by an india-rubber tube to a glass filler, into 
which the water was poured, and from which it flowed down the small tube to 
the front end of the experimental one, and returned to the outside of the box 
by the space between the tubes. In this way the experimental tube could be 
easily heated or cooled, and the space all round it left free for observation. 
For higher temperatures, a fine platinum wire, heated by means of a small 
bichromate of potash battery, was employed. 

Different kinds of dust were used in the experiments, such as dust made 
in the usual manner with hydrochloric acid and ammonia, and by burning 
sulphur in the presence of ammonia; this last was used when very dense 
fogging was required ; smoke of paper and other substances were experimented 
with; also dusts made by burning sodium or magnesium; and for experiments 
with dust which would not change with heat, calcined magnesia and lime 
were employed. Charcoal powder was also used in some experiments. The 
powders of these last three substances were stirred up by means of a jet of 
air. These dusts were also varied by the addition of water vapour. 

Suppose now that the gas is lit in the lantern, and the dust-box in its place 
Let us introduce into the box through the opening in the back one of the glass 
or metal tubes, closed at the front end, and introduce into this tube from the 
back the smaller one, and connect this latter with the filler, so as to enable 
ms to pour hot or cold water through the tube, to heat or cool it. If we 
are going to use smoke, a piece of smouldering brown paper is introduced into 
the box, by removing the glass front, which is kept easily removable for this and 
other purposes; or, if we are going to use sal-ammoniac dust, the ammonia 
and hydrochloric acid can be introduced on glass or wooden rods through 
small openings in the box, or the acid and ammonia may be placed in small 
open ve3sels inside the box. If the dense sulphate dust is required, the sulphur 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 243 

may be placed on a match and introduced into the box after being lighted. 
When the dust is thick enough, and uniformly distributed through the box, 
bring the light to a focus on the tube. For the present the tube must be 
neither heated nor cooled. Using the magnifying glass ; it will in all proba- 
bility be found that there is a clear space all round the tube or on some part 
of it, and that the air currents are carrying off the clear space in an irregular 
manner, or there may be seen rising over the tube a regular dark plane, depend- 
ing on the relative temperatures of the air and the tube. 

Now remove the beam of light from the dust-box and leave it for some time. 
If left long enough, and the box kept free from changes of temperature, it 
will be found that all air currents have ceased, and a close examination of 
the experimental tube will show that the dust is now in contact with it at the 
sides and on the top. But if we look on the under side of the tube we shall 
there see a clear space, like that shown in fig. 1, which represents the tube seen 
endways." It will be observed that this does not agree with Dr Lodge's 
observations ; but I think I have taken every precaution, and the conclusion 
which I have come to is, that bodies have not sharply defined dust-free coats, 
and that when the bodies and the air have the same temperature, the dust 
comes into contact with the sides and top of the bodies. t Now what is the 
cause of this clear space under the tube ? Clearly 

Gravitation, 

which brings me to the first of the causes of the dark plane. When the air 
comes to rest, the temperature of the air and the tube being the same, there is 
nothing to keep the dust from coming into contact with the tube. But gravita- 
tion is at work on the particles, and while the air is still the particles are all 
falling, and as the upper surface of the tube stops those falling on it, there are 
no particles to supply the place of those falling from the space under the 
tube, and the result is that a dustless space is here formed. If now we pour 
into the tube some cold water we can study the 

Effects of Cold. 

At once a downward current is started, and this downward current carries with 
it the clear air under the tube ; the two currents of dustless air from the sides 

* In the figs, the white surface represents the light-reflecting dusty air, while the black represents 
the transparent air, free from reflecting particles. 

t The only reason I can imagine for this difference between Dr Lodge's results and mine is that 
lie worked with more powerful sources of illumination than I did. He used either the sun's light, an 
oxyhydrogen lamp, or a Seerin arcdamp, while I only used gas. Now one result of this difference 
would evidently be that the illuminating beam used by him would bave a much greater heating effect 
than the one used in my experiments, and would therefore heat the surfaces under examination. I 
found this effect even with gas. If the body had a small capacity for heat, it was only necessary to 
keep the light focused on it for a short time to heat it sufficiently to cause a clear space to form over 
the part where the light acted. 



244 Mil JOHN AITKEN ON THE 

of the tubs meet underneath it, and form a dark plane in the centre of the 
descending current, as represented in fig. 2. 

It might be thought that gravitation would not act quickly enough to keep up 
a supply of dustless air sufficient for this purpose. This however does not seem 
to be the case, and gravitation appears to be the only cause of the distribution of 
the dust, causing this dark plane in the descending current. One reason for 
supposing this is, that if we only cool the tube very slightly, the dark plane is 
very thick and well marked; but the more we cool the tube the thinner does 
the dark plane become, intead of thicker, which would be the result if it was 
due to difference of temperature. The effect of the increased cold is to increase 
the velocity of the descending current, and draw out and thin down the dark 
plane. Further, if we closely examine the air round the tube with the strong 
magnifying glass, we shall see the particles of dust descending and settling on 
the horizontal part on the top of the tube, while the particles which fall a little 
to each side of the centre line are carried on by the current, and continue to clasp 
the tube closely till the current begins to turn under the tube, where the particles 
being free to fall, drop away from the tube, and leave a clear space (see fig. 2). 
This clear space only begins to be perceptible when the current begins to turn 
underneath the tube, and gradually becomes thicker as it travels underneath 
towards the centre where the two currents join, and form the descending 
dark plane. 

The rate at which dust settles out of air by gravitation is much quicker 
than we might imagine. Dust is kept in suspension by ascending currents, and 
when these are removed it settles remarkably quickly. There was an oppor- 
tunity for seeing this in these experiments. If the experimental tube was 
cooled, then the cold gave rise to currents descending on the side of the box 
where the tube was, and rising on the other side ; but the rising current only 
came up to the height of the tube, and all the air above the tube was still and 
currentless, because its temperature increased towards the top of the box, and 
then was produced a condition of stable equilibrium. Under these circum- 
stances, I have frequently seen the whole of the upper part of the box above 
the cold tube become quite clear, and with a sharp line of demarcation between 
the clear still air above, and the dusty currents underneath. It is, of course, 
the vertical component of the currents that keeps the dust in suspension, the 
horizontal component having no such action. This may be seen when we 
cause a current of dusty air to flow along the under side of a horizontal flat 
surface. At the point where the current starts, the dust is in contact with the 
under surface of the body, but falls further and further from it as it flows 
along. 

In order to study the effect of temperature alone, it was necessary to 
arrange the experiment so as to get rid of this gravitation effect. For this 
purpose I prepared another piece of apparatus. The ideal shape of body for 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 245 

this purpose would be one having some length and breadth, but infinitely thin 
and flat, so that when placed vertically, the air in passing over it would never 
have to move in a horizontal direction. The nearest approach I could make to 
this was made with a piece of copper foil folded on itself, soldered all round 
its edges, and fixed to the end of a brass tube. It was heated and cooled by 
passing into it hot or cold water. This instrument presented at the front edge 
extremely little thickness, and was found to answer well, but was rather delicate 
and easily put out of shape. As it is only necessary to examine one side of the 
test plane or surface, a different form of apparatus was afterwards adopted. It 
was made of a piece of brass tube the same as used in the previous experi- 
ments, and a flat plate of copper was soldered to one side of it at the front 
end. This plate was filed perfectly flat and smooth, and sharpened at the top 
and bottom edges, all the bevel being on the tube side of the plate. The side 
of the plate presented towards the source of illumination was thus a perfectly 
flat surface, and when placed vertically, the air passing over the front surface 
could not have its dust separated from it by gravitation, as all the horizontal 
movement went to the back of the plate. 

Placing either of these test surfaces in the dust-box with the plate vertical, 
cold was applied. At once a downward current was produced, but no dark 
space was formed on the vertical test surface ; and if the copper foil apparatus, 
which is flat on both sides, is used, no dark plane whatever is formed, as 
shown in fig. 3. More intense cold was tried, and a temperature of — 10° C. in 
air of a temperature of 15° C. was found to produce no effect save an increased 
rate of current, and an increased brightness in the particles near the plate, 
due to water vapour being deposited on them by the lowering of the tem- 
perature, an effect observed by Lord Rayleigh on the dust bounding his cold 
dark plane. Different dusts were tried, and the experiment varied in many ways, 
but when the gravitation effect was removed, not the slightest tendency to the 
formation of a dark plane by cold could be detected. The tendency seemed 
to be the other way. The dust particles in all cases tended to keep close to 
the cold body. This indicates that Lord Rayleigh's dark plane formed in the 
descending current from a cold body is not an effect of the cold, but is due to 
the separating action of gravitation. 

What I am about to state may at first seem a contradiction of this conclusion. 
When varying the conditions of the experiment, and altering the amount of water 
vapour present, I was much surprised to find that under certain conditions the 
dark plane had a decided tendency to make its appearance in the descending 
current even from a thin vertical surface. On repeating the experiment and 
varying it, it was found that the conditions best suited for getting this dark plane 
were when there was nothing but ordinary atmospheric dust in the box, and 
the air was saturated with water vapour. Under these conditions, there was 
generally all through the box a haziness, but in the space in front of the cold test 



240 MR JOHN AITKEN ON THE 

surface the cold thickened this haziness into a dense cloudiness, which extended 
for some distance from the plate and showered down from it. But between 
the fog and the test surface there was a well-marked dark space. To what was 
this due ? I had already satisfied myself that cold did not tend to drive away 
the particles. Then why did these particles conduct themselves differently 
from the others % While the test surface was vertical, the motion of the 
particles was too quick to be followed with the magnifying glass. The surface 
was, therefore, placed nearly horizontal, with a slight slope towards the light 
(see fig. 4). Still the dark space remained, and the current flowed on, but the 
particles did not come close up to the plate, though gravitation was acting on 
them. The cold could surely not be repelling the particles and keeping them 
off the plate. A short examination with the strong magnifying glass, which it 
was now possible to use as the particles were moving slowly enough, showed 
that this was not the case. The particles were seen flowing along in the 
current, but at the same time they were seen falling into the dark space and 
disappearing when they came within a certain distance of the surface. The 
explanation was evident. The surface, by its very low temperature, had robbed 
the air close to it of its moisture, which it deposited on itself in ice crystals. 
Into this cold but drier air the particles evaporated as they fell, and in this 
case the dark plane would contain the dust of the atmosphere, which, however, 
is black, compared with the brilliancy of the surrounding fog. In this case the 
dark plane was produced by 

Evaporation, 

and this explains why it is not visible when artificial dusts are present, the 
larger particles of the artificial dusts not being sufficiently reduced by evaporation 
to make them comparatively invisible. We shall now pass on to consider the 

Effects of Heat. 

For this purpose let us remove the flat test surface from the smoke-box, 
and put in its place a round tube of metal or glass. A glass one is preferable, 
as it permits the illuminating beam to pass through it, and we are thus enabled 
to see what is taking place all round. After the box is filled with dust, leave it 
for some time, till the tube has acquired the same temperature as the air. On 
examination we shall find, as before, the particles evenly distributed, and coming 
close up to the surface of the tube on the top and at the sides, while underneath 
we shall see the clear space produced by gravitation. We shall first examine 
what the effect is of a slight difference of temperature. For this purposi 
we shall pour some slightly heated water through the tube, so as to raise its 
temperature a very little — a degree or two. When this is done the equilibrium 
is destroyed, and currents begin to form. The clear space formed by gravita- 
tion under the tube rises up, closely clasping and encircling the tube in 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 247 

a clustless envelope. The two currents of clear air which started from the 
under side of the tube, reunite at the top after passing round the sides, 
and ascending in the centre of the upward current, form a well-marked dark 
plane (see fig. 5). Here again gravitation seems to be the principal cause of 
the distribution of the particles. This certainly is the case when the difference 
or temperature is very slight, but we shall see that, as the temperature rises, the 
gravitation effect bears a less and less proportion to the heat effects, which we 
shall presently consider. It will be as well to note here the difference in the 
clear space surrounding the tube in this case and when cold was applied, as 
shown in figs. 2 and 5. When cold was applied (fig. 2), the dark space was only 
on the under side of the tube ; but with heat it is all round the tube, because it 
has its origin in the air under the tube. 

When making these experiments a somewhat peculiar effect was often 
noticed, which seems worth recording, as it forms a good illustration of the 
influences at work here. If, after the tube had been warmed and a well- 
marked dark plane formed over it, no more hot water was added, and 
the tube allowed to cool, the upward current became sluggish after a time, 
and the dark space presented the appearance shown in fig. 6. The two sides of 
the tube now differed. The left side was bounded by a clear space, which 
ascended as before, but on the other side, the dark space did not continue to 
the top of the tube. As shown, the particles here came into the dark space 
and obliterated it. The explanation of this peculiar effect, which so often 
repeated itself, is this. The falling temperature had allowed the current on the 
right side to become so slow that gravitation had time to act on the particles 
after the current turned to the upper side of the tube, and the particles had 
time to fall through the clear space before they were carried into the ascending 
current over the tube. In other words, gravitation undid on the upper part over 
the tube what it did at the under. The left side of the tube continued to keep 
its clear space, because the light used for illuminating it was focused on this 
side; it, therefore, was slightly warmer than the other. 

Gravitation, while it explains the formation of the dark plane in such cases 
as above described, where the difference of temperature is slight, is evidently 
not the whole explanation. Gravitation can obviously have little to do with 
the formation of the dark plane formed over a thin wire, as the time occupied 
in horizontal movement when going round so small a body is not enough for it 
to have any appreciable effect. In order to study the effects of heat apart from 
those of gravitation, the tube with the flat surface fixed on it, employed in the 
experiment with cold, was used, as it eliminates the gravitation effect and 
shows the heat effect alone. Fixing this piece of apparatus in the smoke-box 
with the test surface carefully adjusted in a vertical plane, heat was slowly 
applied to it. An upward current at once started, and it was noticed that at 

VOL. XXXII. PART II. 2 T 



248 MR JOHN AITKEN ON THE 

the same time a clear space was formed on the hot surface, and rose up from 
it, producing a dark plane in the ascending current (fig. 7). This clear space 
was evidently entirely due to the heat in some way driving the particles away 
from the hot surface. 

When working with this flat test surface it is necessary to be careful about 
the adjustment of it in a vertical plane. If the surface leans either to the one side 
or to the other, a clear space is, of course, formed on the side to which it inclines 
by the separating action of gravitation, and gravitation also acts on the particles 
on the other side, and tends to counteract the effect of the heat. Further, if 
the surface is inclined enough, the gravitation effect overcomes the heat effect, 
and destroys the dark space by causing the particles to fall towards the hot 
surface. At the same time, the gravitation dark space on the under side 
becomes thicker and thicker the more the plane of the test surface approaches 
the horizontal. This instrument may be made capable of measuring the relative 
effects of different temperatures, &c, by providing it with a scale to indicate its 
angle with the vertical. The greater the angle at which the dark space is 
visible the greater will be the repelling force. 

By the construction of the instrument, when placed vertically, the gravita- 
tion effect is entirely removed. The dust particles can be seen coming straight 
up, and no purified current coming from the under side (compare figs. 5 and 7). 
The clear space begins to show itself with a very slight rise of temperature. 
Indeed, it would appear that it is formed by the slightest rise of temperature, 
as it always begins to be visible just when the temperature is high enough to 
cause an ascending current, With a slight difference of temperature it is 
extremely thin, and requires careful observation to detect it, but as the tem- 
perature rises it becomes thicker and thicker. For the present I shall not enter 
into the question as to why the dust particles move away from a hot body, but 
shall leave the consideration of this subject till after describing some experi- 
ments which seem to throw some light on the mechanism of these movements. 
For the present I shall simply speak of it as repulsion due to heat. 

The following experiments will help us to understand the action of this 
repulsion. Fix a piece of glass in front of, and parallel to, our flat test 
surface, and at a distance from it of two or three millimetres. Glass is used 
because it is transparent, and allows the illuminating beam to penetrate and 
show us what is taking place at the different surfaces. If we now warm the 
test surface, the dust particles all move away from it towards the glass plate, and 
many of them attach themselves to the glass. ^ After a short time the glass 
gets warmed by radiation, &c, from the hot test surface. If we now cool the 
test surface a change takes place, the dust particles move away from the glass, 
and crowd up towards the colder test surface. 

A better form of the experiment is shown at figs. 8 and 9. A glass plate 






FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 249 

A, 12 cm. long and about 4 cm. broad is attached by means of cement, near its 
upper end, to a metal tube, to enable us to heat it while in the dust-box. 
Another plate of glass B, of the same size as A, is placed opposite and parallel 
to it, at a distance of about 5 mm. The plate attached to the tube is first put 
in its place in the box, and after it has acquired the temperature of the air, 
the other plate B is warmed and put in its place, opposite to A, as shown in 
sketch. The box is now filled with dust. If we now carefully examine the 
air between the two glass plates, we shall find that the warm plate B (fig. 8) is 
bounded on each side by a clear space, its high temperature having driven all 
the dust particles to a distance, while the other plate has no clear space round 
it. Now let us put a little warm water into the tube to heat the upper part of 
the cold glass plate A, and note the change in the distribution of the dust. 
As before, the lower part of B is bounded by a clear space (see fig. 9), but the 
upper part of A being now warmer than B, the dust is driven from A towards B, 
and a clear space opened in front of the hot part of A, while the clear space 
formerly in front of the upper part of B is closed. The heat has thus caused 
the dust particles to move across the direction of motion of the air. These 
experiments have been made with different dusts, and always with the same 
result. 

For the purpose of studying the effects of higher temperatures than that of 
boiling water, a fine platinum wire was fitted up inside the dust-box and heated 
by means of a small bichromate battery. The arrangement of wire which I 
prefer for this purpose is made by bending it into a U-shape and bringing the 
two legs close together, say one or two millimetres apart. The wire is placed 
horizontally in the dust-box, with the bend to the front, and the legs at the same 
level, the two copper wires to which it is attached being carried backward and 
out of the box. By this arrangement a clear end-view is obtained all round 
the wire, and the effect of the heat conveniently observed, and further, the 
Avire doubled in this manner, tells us more than a single wire can. 

In experimenting with this arrangement of apparatus, the results are as 
varied as the dusts employed. Each dust gives a different size of dark plane 
for the same temperature. The previous experiments with less intense heat 
seemed to point to repulsion as the cause of the clearing away of the particles. 
If this were the case, it seemed very unlikely that some dusts would be 
repelled further away than others, at least to the extent that actually took 
place. To see if repulsion was the explanation in this case also, instead of a 
single wire, which I used in my first experiments, I doubled the wire into a 
U-shape, as already explained, and placed the length horizontally, with the legs 
at the same level. When this wire was heated in the sal-ammoniac or in sulphate 
dust, it was at once evident that repulsion was not the cause of the dark plane 
in these dusts. With either of them, when the temperature of the wire was not 



250 MR JOHN AITKEN ON THE 

very high, the dark plane rising over each leg was very thin (see fig. 10), but as 
the temperature rose, the planes extended on each side till the two planes met and 
formed one large one (see fig. 11). An examination by means of a magnifying 
glass showed that this broad dark plane was clue to the evaporation, or to the 
disintegration of the particles, as they could be seen streaming upwards and 
disappearing into the dark space under the wires. They there arrived at a 
space the temperature of which was sufficient to convert them into gases or 
vapours. The dark plane in this case was thus due to a change of the particles 
from the solid to the gaseous state. Hence the great differences in the size of the 
dark planes of different dusts, each kind of dust having a different temperature 
at which it evaporates or becomes disintegrated. The sulphate dust, for instance, 
gives a smaller dark plane than the chloride, because the sulphate requires a 
higher temperature to drive it into the gaseous state than the chloride. 

This result is quite different from that got with temperatures which were 
not sufficient to vaporise the particles and make them invisible. It was there- 
fore now desirable to make experiments with some substance which a high 
temperature could not destroy. For this purpose I selected calcined magnesia 
and calcined lime, also soda and magnesia dusts, produced by burning the metals. 
With these dusts a different result was obtained. A high temperature had no 
other effect than forming a thin dark plane over each wire (see fig. 10). But 
even these stable forms of dust were subjected to a repulsion, the particles 
passing near the wire being driven to a small distance from it on each side. It 
may be possible that some of the particles of these dusts are vaporised, but if 
so, the amount must be very small, and can have but little influence on the 
formation of the dark plane. 

Another effect noticed in these, and in the experiments at lower tempera- 
tures, was that whenever there was much water vapour present, there was a 
faintly indicated dark plane formed by the evaporation of the water from the 
particles. If nothing but the dust of the air was present in a fog formed with 
steam, then the wires were surrounded by a very thick dark plane, due to the 
evaporation of the fog particles ; and if any artificial dust was present, then the 
thick dark plane was still visible, but not black, as the particles were only 
reduced in size by the evaporation of the water from them. All these different 
effects of the hot wire can be illustrated at one time, if we put into the dust- 
box some indestructible dust, also some sal-ammoniac and sulphate dusts, in 
proper proportion, and then add some water vapour. When the wire is heated 
in such a mixture, we get a result like that shown in fig. 12. In the centre we 
have the true dark plane, in the wider space there is only the indestructible 
powder present. The next boundary shows the vaporising zone of the sulphate, 
1 he next the vaporising zone of the sal-ammoniac dust, and the last that of water. 
In fig. 12, a is the true dark plane, in which there is nothing but gases and 






FORMATION OP SMALL CLEAR SPACES IN DUSTY AIE. 251 

vapours ; in the wider space b, both the chloride and sulphate dusts are 
vaporised, and we have nothing visible save the indestructible dust ; in the 
next space c the chloride is vaporised, and there are present the sulphate and 
indestructible dusts ; while in the space d all the dusts are present, but dry, 
the condensed water being evaporated. 

Conclusion. 

The conclusion we have arrived at from these experiments is, that for the 
formation of the dark plane in dusty air, there are various causes which may 
be classed under the following heads : — With cold, producing the downward 
dark plane, we have — 1st, the distributing effect of gravitation; and 2nd, the dis- 
appearance of the particles by evaporation, when falling into a space rendered 
dry by condensation produced by cold. With heat, producing the upward dark 
plane, we have — 1st, the distributing action of gravitation; 2nd, the distributing 
action of repulsion due to heat ; 3rd, evaporation of the particles ; and 4th, dis- 
integration of the dust. In the last two cases the dust is rendered invisible by 
the heat changing it from the solid light-reflecting condition to the transparent 
gaseous state. 

Effect of Centrifugal Force. 

We may here ask ourselves, Are these the only ways in which the dark 
plane may be produced ? It is, of course, impossible to give a definite answer 
to such a question. There are, no doubt, other ways in which it seems possible 
that this phenomenon might be produced, and it seemed worth while to consider 
Lord Bayleigh's suggestion as to the effect of centrifugal force. On consider- 
ing the action of this force in the experiments described, it is evident that it 
can have but little to do with the distribution of the particles, because the air, 
in rising and passing round the wires and tubes, is curved first in one direction, 
and before it again takes up its original direction of motion, it is curved to an 
equal amount in the opposite way. So that whatever sifting action the centri- 
fugal force may have at the one part of its course, will be undone at the other. 
I, however, thought it worth while to arrange an experiment, to see if the par- 
ticles really were thrown out by centrifugal force at any part of their passage. 
With this object, I fixed inside the dust-box a piece of thin sheet metal, with 
its plane vertical. Arrangements were made so that a current of dusty air was 
caused to flow down the one side of the plate, round the lower edge, and up 
the other side. In this way the air was caused to curve through, an angle of 
180°, and no curving in the opposite direction took place. When this was 
done, it was seen to be possible to give an appearance very like as if the cen- 
trifugal force did throw the particles away from the centre of motion. In front, 
md just above the lower edge of the plate, there was formed a clear space, 



252 MR JOHN AITKEN ON THE 

very near the centre of rotation of the air. On examination, however, it was 
seen that this was caused by an eddy, due to the upward channel in which 
the air was confined being wider than the space under the plate. In the eddy 
so formed the particles were soon sifted out by gravitation, and a clear space 
formed. On contracting the breadth of the upward channel, and making it 
equal to the passage under the plate, this eddy disappeared, and the clear space 
was no longer formed. In this experiment, though the air was caused to curve 
through a considerable angle, yet there was no satisfactory evidence of any 
distributing action due to centrifugal force. It seems probable that, even 
under these conditions, a certain amount of sifting action does take place, 
though not enough to make it observable ; and though there are reasons 
for supposing that if the particles were heavy enough, and the velocity of 
the current great enough, there would be a visible effect, yet it is evident 
that centrifugal force plays no part in the formation of the dark plane, in the 
experiments with heat and cold. The fact that the dark plane has a sharply 
defined boundary is proof that centrifugal force is not the cause of the distri- 
bution, as this force would not give such a result. Its tendency would be 
to throw the heaviest particles furthest out, and thus give rise to a shaded 
outline. 

Effect of Electricity. 

Electricity is another force which might be supposed to play some part in 
the formation of the dark plane. It was difficult to believe that the attraction 
of the particles was a thermal effect when making the experiments with the hot 
and cold surfaces placed opposite each other, and observing the way in which 
the particles were repelled by the one plate and attracted to the other ; and on 
making other experiments, which will be presently described, in which the dust 
rising in the current from the heated platinum wires was attracted to, and 
deposited itself on, the surfaces of bodies placed in its path. The dust particles 
conducted themselves in a way strongly suggestive of electrical disturbance. They 
seemed to be attracted by the cold surfaces in exactly the same way as if they 
had become electrified at the hot surface. It was, therefore, thought advisable 
to make experiments to ascertain whether electricity had anything to do with the 
formation of the dark plane. Experiments were first made to see if the hot sur- 
face became electrified in the dust-box by the passage of the air over it, or from 
other causes. For this purpose I used a small cylindrical conductor of solid 
metal, about 1 cm. in diameter, and with rounded ends. This conductor was 
fixed to the end of a glass tube, and a conducting wire connected to it and 
carried through the tube. The conductor was then introduced into the dust- 
box through an opening in the back, after which its connecting wire was joined 
to a gold-leaf electroscope. Before the conductor was put in its place it was 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 253 

heated, and the box was filled with dust. Examined with the magnifying glass 
in the usual way, the dark plane was found to be well marked and the repulsion 
going on as usual, but not the slightest sign of electrification showed itself at 
the electroscope. No signs of electricity having shown themselves at the hot 
surface, it was sought for in the ascending current. This was done by first 
removing the insulated heater and putting in its place the platinum wire, to get 
a more intense effect from the high temperature. Over the wire was placed a 
large insulated flat-shaped conductor for the dust to deposit itself upon. The 
conductor was then connected to the electroscope, the box filled with dust, and 
the electric current turned on to heat the wire. The leaves of the electroscope, 
however, remained close together, so that the dust deposited on the conductor 
could not have been charged with electricity. 

It may be objected to these experiments that the electroscope used was not 
sensitive enough for the purpose, and that if a more sensitive instrument had 
been employed, signs of electricity might have been obtained. It is quite 
possible that another instrument might have shown signs of electrical disturb- 
ance, but I think that if electricity was the cause of these phenomena, and was 
sufficiently strong to repel the particles and to cause them to adhere to bodies, 
it would be quite powerful enough to separate the leaves of the electroscope. 
Any electrification less than would affect the leaves would only be a secondary 
matter, and could not be the cause of the phenomena. Another reason for 
supposing that electricity has little to do with these effects is that the dust tends 
to settle only on cold surfaces. 

Experiments were now made to see what the effect is of electrifying the hot 
surface. The small cylindrical conductor was heated, placed in the box, and 
connected with the electroscope. A Leyden jar charged very slightly, but 
enough to cause the full divergence of the leaves of the electroscope, was then 
connected with the apparatus, and the effect on the dust surrounding the electri- 
fied conductor noted. While the body was hot enough to cause a well-marked 
dark plane, there was not the slightest effect produced by the electricity, though 
the leaves of the electroscope were wide apart, and showed that the hot surface 
had a decided charge. The electroscope was then removed, and a much higher 
charge given to the conductor. This time an effect was evident, but it was 
difficult to say what was taking place. The general appearance of the air round 
the hot conductor had quite changed. The sharp outline of the clear space 
round it was destroyed, and the dark plane over it had lost its clear and sharp 
outline, and had become much thicker, though not so dark, as before. All 
round the conductor there seemed to rage miniature storms, and the particles 
had much the appearance as if they were seen all out of focus. This effect was 
produced by either positive or negative charge. 

To find out what was taking place in the air round the electrified body, I 



254 MR JOHN AITKEN ON THE 

had recourse to large-sized particles of dust to enable me to follow the move- 
ment of each particle. Calcined magnesia was selected for this purpose. 
When the air in the dust-box was filled with this powder, the reason of the 
change in the dark space at once became evident. The particles in the ascend- 
ing current could be seen rushing towards the electrified surface and adhering 
to it. The dark space was thus broken in upon, and its outline destroyed 
by the attracted particles ; the air round the body was at the same time 
deprived of a great quantity of its dust ; and over the conductor there rose a 
thick and ill-defined band of clearer air, the particles which formerly were in it 
having attached themselves to the electrified body. All the particles did not 
seem to be equally attracted, but some much more than others. This gave rise 
to the irregular movements seen all round the body. The dust particles 
frequently deposited themselves on the conductor in small needle-like radial 
columns, which grew by the addition of the particles till they got to a certain 
size, when they were shot off" and flew through the air with surprising velo- 
city. If, after the conductor had been electrified a short time, the supply of 
electricity was cut off and the conductor connected with the electroscope, the 
charge given to the air and the dust in the box was given back. The leaves of 
the electroscope expanded quickly, and if discharged, rapidly became charged 
again, the dust at the same time being attracted to and deposited on the con- 
ductor in needle-like columns. 

After looking at this last experiment, and seeing the tendency which particles 
in electrified air have to deposit themselves on bodies, we cannot help asking 
the question, Does this experiment throw any light on the well-known tendency 
to the development of certain forms of bacteria resulting in the putrefaction of 
our foods, and in the appearance of increased quantities of certain ferments 
during thundery weather ? Can it be that the germs of these forms of life 
floating in our atmosphere have a far greater tendency to settle upon the 
surface of bodies from electrified air than when there is no electrical disturb- 
ance 1 No doubt this electrical attraction must have some effect in this 
direction, but whether it is the principal cause or not I shall not venture 
to say. 

If we use still higher degrees of electrification than those used in the above 
experiments, other effects are produced, but they have no relation whatever to 
the formation of the dark plane. From the experiments described it will be 
seen that the effects of electricity are of quite a different kind from those of 
heat. The electrified body, instead of repelling the particles like a hot one, 
attracts them, and clears the air in a partial way by attracting some of the par- 
ticles to itself, while heat acts by repelling all of them to a distance. This anta- 
gonism between the two forces maybe illustrated by heating the conductor and 
electrifying it slightly. At first no effect is produced by the electricity ; the 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 255 

dark plane remains quite clear, but as the temperature falls, a stage is arrived 
at when the electrical effect overcomes the heat effect, and the particles break 
in on the dark space and destroy it. 

In making electrical experiments, most of us have noticed the tendency which 
dust in the room has to settle on the different parts of the electrical apparatus, 
and to destroy the insulation, and many have noticed the excited and rapid 
movements of electrified dust. Dr Lodge, in the letter already referred to, 
remarks on the rapidity with which the dust-box, in his experiments, was cleared 
of its dust by means of electrified bodies placed inside it. I have made some 
experiments on this subject, to determine the conditions most favourable for the 
clearing of air by means of electricity. For these experiments I preferred to 
use a large glass flask about 30 cm. in diameter. Placing this flask with its 
mouth downwards, I introduced into it an insulated metal rod, fixed vertically, 
and passing through the open neck of the flask. If a dense cloudiness was 
made in the flask with any dust, by preference it was generally made by burn- 
ing sulphur and adding a little ammonia. After a dense whiteness had been 
produced, the conductor was electrified. Seen from a distance, no change 
seemed to have taken place, but on examination it was found that all the dust 
was deposited on the inside of the flask in a nearly uniform white coating. To 
enable me to see what was taking place, the inside of the flask was wetted. 
When the electrification began, the dust could now be seen driven about 
as by a violent wind, and, after a few turns of the machine, it had disap- 
peared from the flask. The conditions found most suitable for producing this 
result quickly were a rapid discharge of the electricity into the dusty air by 
means of a point or points. If the conductor terminates in a ball inside the 
flask, the electrification has but little effect. In addition to the conductor 
terminating in a point, it is also necessary to have near the electrified point 
surfaces to aid in the rapid electrification of the dust. When the point is 
surrounded by surfaces the air currents are violent, but if we remove the sur- 
faces the currents are not nearly so strong. This may be seen by allowing a 
cloud of dust to rise round a conductor placed in an open space, when but little 
effect will be observed on electrification. After the dust has been electrified, 
it ought to be brought near some surface, towards which it may be attracted, 
otherwise it may lose its charge before meeting a place to deposit itself. 

Experiments have also been made to determine whether the very fine and 
invisible dust of the atmosphere is also caused to deposit itself when electrified. 
With this object the large glass flask had an india-rubber stopper fittei to it, 
through which passed a tube to connect the interior of the flask with an air- 
pump, to test the condition of the air in the flask by reducing its pressure, 
while it was kept moist by the presence of water, and to observe whether any 
cloudy condensation took place after electrification. A conductor insulated in 

VOL. XXXII. PART II. 2 U 



2.36 MR JOHN AITKEN ON THE 

a glass tube passed through the stopper, and terminated in a point inside the 
flask. Means were taken to insure the insulation of this conductor inside the 
flask. This was done by surrounding the insulating tube with another tube, and 
causing the entering dry air to pass into the flask through the space between 
the tubes. The insulation was thereby kept good, and the glow of the dis- 
charge at the point was quite visible in the midst of the moist air. 

On experimenting with this apparatus, it was found that electrification for a 
short time by means of an ordinary cylindrical electrical machine was sufficient 
to deposit almost all the dust, only the very slightest signs of condensation being 
visible after electrification. What formed the nuclei of the very few cloud par- 
ticles which appeared it is difficult to say. Whether they were undeposited dust 
particles, or particles thrown off the conductor, or some product of the electric 
discharge, this experiment does not determine. That they may be some pro- 
duct formed from the air by the electric discharge is suggested by the following 
experiment. First purify the air in the flask, either by passing it through 
a cotton-wool filter, or by electrification, then reduce the pressure to super- 
saturate it, and now electrify. At once a cloud forms all round the conductor, 
and extends to near the sides of the vessel. This cloud is evidently not 
formed by anything thrown off the conductor, forming nuclei, as it appears at 
the same moment all round the point. It is more probable that the nuclei of 
these cloud particles are formed by the discharge of the electricity producing 
in the air nitric acid, or ozone, on which the supersaturated vapour condenses. 
That the nuclei so formed are not solid particles there seems to be but little 
doubt, because if we allow filtered air to enter so as to increase the pressure 
and evaporate the particles, cloudiness does not reappear on again reducing 
the pressure, which it certainly would do if the nuclei had been solid particles. 
The number of nuclei that remain after electrification is very small, if the air 
is not supersaturated with vapour ; and practically we may say that electrifica 
tion deposits all the very fine dust, and I may remark here that it does it in a 
very rapid manner. The air in the flask can be purified much quicker by means 
of electricity than by the air-pump and cotton-wool filter. It may be noted 
here that the dust of the atmosphere has but little effect on the brilliancy 
of the glow of the point discharge. With a large amount of dust, with the 
ordinary dust, with no dust, and with the electrification used, no difference 
of importance in the brightness of the glow was detected. 

The Lungs and Dust. 

When we see a beam of sunlight shining into a darkened room through a 
small opening, and revealing, by illuminating, the suspended dust, making the 
beam look like a solid body, we have great difficulty in realising that our atmo- 



FORMATION OF SMALL CLEAR SPACES IN" DUSTY AIR. 257 

sphere can be so full of dust, as this experiment shows it to be, as it escapes our 
observation under ordinary conditions of lighting, and it gives us a feeling of 
discomfort to realise that we are breathing that dust-laden air. This uneasiness 
was by no means decreased when my experiments on cloudy condensation 
revealed the fact that, in addition to that mass of visible dust, there are enormous 
multitudes of particles so small that even the concentrated light of the sun does 
not reveal them. These minute particles are so numerous that hundreds of them 
are crowded into every cubic centimetre of air. On realising these facts our 
feelings are those of wonder that our lungs can keep so clean as they do, while 
such vast quantities of impurities are constantly ebbing and flowing through 
them. At that time I was not aware that there is an influence ever at work tend- 
ing to protect the lungs by preventing, to a certain extent, the particles of dust 
coming into contact with their surfaces, — that nature had provided a subtle form 
of mechanism possessing some of the advantages of a filter without any of its 
disadvantages. The experiments here described show that a hot surface 
repels the dust particles in the air. The heat of our bodies will, therefore, 
exert a protective influence on the lungs, and tend to keep them free from 
dust. 

Our lungs, however, are not only hot, they are also wet. What influence 
will the constant evaporation which takes place at the surface of the tubes 
and passages have on the dust? To answer this question, I fitted the flat test 
surface in the dust-box, and through an opening in the top introduced a brush 
dipped in water, with which one-half of the surface was kept wet, the other half 
being dry, to compare the effects under the two conditions. When the surface 
was heated a few degrees, to even less than the temperature of our bodies, the 
result was most decided, the dust being driven more than twice as far from the 
plate in front of the wet part as it was from the dry. The evaporation, there- 
fore, of the water from the surface of the bronchial tubes tends strongly to 
ward off the dust, and keep it from coining into contact with their surfaces. 
We must not, however, imagine that the heat, or the heat and the evaporation, 
are sufficient entirely to prevent the dust coming into contact with the surfaces 
of our bronchial tubes and passages, because dust really does come into contact 
with them, but it does not do so nearly to the extent to which we have been in 
the habit of supposing. 

The necessary conditions for this repulsive effect to be active are, that the 
air is acquiring heat and moisture. If the air has the same temperature as 
our bodies, and is saturated with vapour, this force no longer exists, and gravi- 
tation and other forces are free to act. 

Although the repulsion due to heat and evaporation are not powerful 
enough to form a perfect protection to the lung surfaces against the contami- 
nation of dust, yet it is very evident that their protective influence will have a 



258 MR JOHN A1TKEN ON THE 

most important effect on the condition of our lungs, and one towards which I 
wish to direct the attention of those who make this organ a special study. 
There seems to be but little doubt that we have here an explanation of some of 
the effects of different climates. For instance, what a difference there must be 
in the amount of dust deposited on the lungs from air breathed at, say, St 
Moritz or Davos Platz, and at such places as Madeira or other similar health 
resorts ! These remarks are altogether apart from the question of the amount 
of dust in the air at the different places, and refer only to the action of the 
lungs on the dust which maybe present.* In the Alpine resorts the air is cold 
and dry, and the tidal air, which flows backwards and forwards through the 
bronchial tubes, is in the very best condition for preventing the dust coming into 
contact with their surfaces, as the difference in temperature between the air 
and the body is great, and the air is also capable of causing a rapid evaporation. 
Whereas, at such places as Madeira, where the air is hot and moist, the repelling 
forces are both at a minimum. The effects of these different conditions on the 
lungs seems well worth study. 

In illustration of the protective influence of heat and moisture many experi- 
ments may be made, but the following is perhaps the easiest. Take an ordinary 
paraffin lamp, raise the flame till a very dense cloud of smoke rises from it. 
Over the lamp place a very tall metal chimney, to produce a quick current 
of air and also to cool it. Have ready two porous cylindrical jars (porous 
jars are used because they keep up a supply of water for evaporation), one 
jar filled with water slightly heated, and the other with cold water. Cover 
both jars with wet white paper. Now introduce the hot one into the top of the 
chimney, and leave the black wreaths of smoke to stream over it for say half a 
minute, then take it out and put in its place the cold one, and leave it for the 
same length of time. The result will be, the hot one will be quite clean, not a 
speck of soot on it, while the cold one is covered with soot. It is not, however, 
so black as a cold dry surface would be, as the slight evaporation from its 
surface tends to protect it. 

We must not, however, suppose that the lung surfaces are so well protected 
as the paper in this experiment. In the lungs the currents are quicker, 
they do not flow over such uniform surfaces, and further, they pass round 
curves, so that in the lungs dust tends to deposit where the currents flow 
quickly where they strike on the concave side of curved passages and on pro- 
jecting edges. Further, all dust which penetrates beyond the tidal air and gets 
into the residual air will ultimately fall on the surfaces of the tubes and air- 

■ The amount of dust breathed by invalids at the two places will not be greatly different, Bfl 
most of their time is spent in the house, and the air in the rooms at the two places will be nearly 
equally dusty. The higher temperature inside will slightly reduce the thermal effect, but will not 
diminish the rate of evaporation. 




FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 259 

cells. This tendency of the dust in the residual air to settle is increased by the 
load of water deposited on it by the moist air. 

The amount to which our lungs are protected by heat and evaporation can 
scarcely be solved in a physical laboratory, and will be best determined by 
anatomical examinations of lungs which have lived under different conditions of 
temperature and moisture. 

A Thermic Filter. 

Having observed that the dust particles tended to move away from hot 
bodies and to attach themselves to cold ones, I made some experiments 
on the subject to study the movements of dust particles when placed between 
hot and cold surfaces. Most interesting results were obtained by placing near 
the hot platinum wires, already referred to, a piece of glass or a plate of metal, 
and getting the dust deposited upon it. One arrangement of the experiment 
is to place the glass with its plane vertical and transversely over the wires, 
at such a height that its lower edge almost touches the wires, and fill the 
box with dust by blowing up some calcined magnesia or other fine powder. 
After all the currents have settled, and while the air is still full of dust, the 
electric current is turned on and the wire heated. A well-marked dark plane 
at once rises over the wire, and in its upward passage it is cut transversely 
by the glass plate. After the plate has been left for some time with the air 
current streaming over its surface, it is found to have a very beautiful impres- 
sion of the dark plane imprinted on it. The warm air, in streaming upwards 
over the surface of the glass, deposited its dust on it, and the fact of there being 
no dust in the dark plane is recorded by a well-defined line of clear glass, 
the deposit of dust on each side of the clean line being thickest just along 
the edge, and thinning away on each side. These impressions of the dark plane 
may be made permanent by causing the dust to be deposited on a plate newly 
coated with black varnish, and used while the varnish is still soft. 

Tt is not necessary to put anything on the surface of the glass to cause the 
dust to adhere, as it attaches itself to a clean surface of glass with considerable 
firmness, but some adhesive substance on the plate enables the impression to 
stand rougher treatment. Impressions of the dark plane have also been made 
with charcoal dust deposited on opal glass. These black impressions are, of 
course, " negatives " of the magnesia ones, the plane in the former case being 
white, surrounded by black dust. The charcoal dust was securely fixed by first 
coating the glass with a thin solution of gum, which was dried before the 
dust was deposited on it, and the dust fixed by breathing on the surface. 

If in place of putting a plate vertically over the wires, we place two plates 
vertically — one at each side of the wire — we then get the dust deposited on the 
plates, thickest opposite to the wires and thinner higher up. Arrangements 



260 MR JOHN AITKEN ON THE 

were made for studying the action of surfaces placed on both sides of the wires. 
Fixing the plates parallel to each other, and at a distance of 2 or 3 mm. apart, 
with the platinum wire between them, I carefully watched the motions of the 
particles carried up in the air current. As the particles approached the wires 
they gradually changed the direction of their motion, and instead of coming 
straight up they curved towards the sides, some of the particles striking and 
adhering to the side plates at a point below the wire. Some rose higher and 
stuck opposite to it, others went higher still, while others passed on to the top 
and escaped. 

I had for some time been trying to arrange an experiment in which I should 
be able to watch the movements of the individual particles of dust, so as to see 
them moving away from the hot surface. My intention was to examine the 
movements of the particles with a microscope of low power, or with a powerful 
magnifying glass. My great difficulty, however, was to get the movements 
due to the convection currents sufficiently slow to enable me to follow the 
moving particles when much magnified. After making the experiment last 
described, I saw it was possible to arrange for this much- desired observa- 
tion. The use of the large particles of magnesia enabled me to dispense with 
the microscope, and use only a magnifying glass of moderate power ; and by 
bringing the plates on each side of the wire close together, the velocity of the 
upward convection current could be greatly reduced by the friction of these 
surfaces, and by their cooling effect on the gases. The two side plates of glass 
were accordingly brought closer together, to a distance of about 1 millimetre. 
Fig. 13 represents the arrangement magnified five times, the U-shaped wire 
being shown in section between the plates. The ascending current was now 
very slow, and no difficulty was experienced in following the movements of the 
individual particles, so I had at last the satisfaction of seeing the particles 
being repelled by the hot wire. 

When the wire, heated to a red heat in air filled with magnesia dust, was 
examined by means of a magnifying glass, the spectacle which presented itself 
was most curious and interesting. At a distance below the wires, the particles 
could be seen coming straight up between the glass plates, but as they approached 
the wires they seemed to get uneasy, and as if wishing to avoid the heat, 
some of them attached themselves quickly to the glass, others went further up, 
but soon curved towards the sides and adhered to them; while others boldly 
advanced straight up, almost to the wires, when their motion was suddenly 
arrested and they were driven downwards and sideways, and attached themselves 
to the glass. If the wires were hot enough, not a single particle got past them, 
and the glass plates had each a patch of magnesian powder adhering to 
its surface below the level of the wires. The direction of movement of the par- 
ticles is roughly indicated by the lines in fig. 13. 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 261 

These experiments naturally suggested the possibility of constructing 
an air filter on thermic principles. They showed that the visible particles 
of dust could be thrown out of the air, as the particles tended to move from 
the hot parts, and to attach themselves to cold surfaces. But the question 
which naturally suggested itself was, Are the very small invisible particles also 
arrested ? If the thermic filter turned out to be a success, it appeared to 
me it would also be the best way to get an answer to this question. In order 
to filter air on thermic principles, all that appeared necessary was to pass the 
air through a space or channel, the two sides of which were kept at different 
temperatures. In this way I hoped the dust would be driven from the hot 
side and attach itself to the cold one. Practically to carry out this idea, the 
simplest method that suggested itself was to pass the air through the space 
between two concentric tubes, the one tube being kept hot, and the other cold. 
In the preliminary instruments which have been made, the distance between 
the tubes forming the space through which the air passes, is in one instrument 
less than 1 mm., but in other instruments this space is nearly as much as 3 mm. 
The length of the passage in the different instruments is about 35 cm. One of 
these instruments has the outer tube jacketed by means of a larger pipe for the 
purpose of heating it with steam. The other instruments were heated simply 
by means of a gas flame. The filter is shown in section, fig. 14. A is a tube 
about 13 mm. diameter. B is another tube slightly larger, and allowing a space 
C, between the two for the passage of the air to be filtered, which enters and 
leaves by the tubes D, D. The outer tube E forms a steam jacket round B. 
F, F are pipes for steam entering, and for condensed water leaving the jacket. 
The pipe A is kept cold by means of a stream of water. In working the instru- 
ment it is not, however, necessary to keep to this arrangement ; steam may be 
admitted to the centre tube A, and cold water to the outside jacket ; both 
arrangements do equally well. For the purpose of cleaning and examining the 
surfaces of the air channel, the centre tube was not permanently fixed in its 
place, but was so arranged that it could be easily taken out, and the joints 
were made tight by means of the short pieces of india-rubber tube H, H. The air, 
after passing through the space C, was conveyed by means of a tube to a glass 
flask, in which there was a little water. The flask in turn was connected by 
means of another tube to an air-pump, in order to test the condition of the 
air after passing through the instrument. If cloudy condensation is produced 
when the pressure is reduced in the flask, we know that the air is not filtered; 
and, on the other hand, if the air remains perfectly clear on exhausting, we 
know that no dust, not even the invisible particles, have passed into it. 

The apparatus was fitted up for trial, all the connections being made and 
tested. Using the instrument heated with flame, the first effect of the heat, 
as expected, was a great increase in the fogging. The temperature was raised 



262 MR JOHN AITKEN ON THE 

as high as it safely could be, to cleanse the instrument thoroughly ; after which, 
as we know, it will cease to give off nuclei at a lower temperature. When the 
tube was thoroughly cleansed by means of heat, and all the impurities swept 
out of it by a current of air, the temperature was lowered slightly, and the air 
allowed to pass slowly through the tube on its way to the test-flask. After 
this, the fogging in the flask gradually diminished, and after passing through 
the rainy stage, it ceased entirely, proving that the filter was doing its work 
thoroughly, not a single particle— not even one of the very minute and invisible 
ones— escaping it. On equalising the temperature, either making both tubes 
hot or both cold, the filtering action of course ceased. 

It does seem somewhat strange that air should be freed from all its 
dust in passing through a channel large enough for a fly to pass, if it has 
sufficient intelligence to keep always on the cold side. All who have 
experimented on this subject know that dust can get through any opening, 
however small. On testing this filter for the first time, I failed to get a satis- 
factory result. I however felt convinced that it ought to work, and the 
failure was attributed to some imperfection in the tubing or joints. Arrange- 
ments were therefore made for testing the tightness of the whole apparatus. 
The one end of the filter being connected, as described, to the glass flask in 
which the air was tested, I now connected a cotton-wool filter to the other 
end of the thermic filter, and proceeded to test if all was tight, by drawing in air 
from the cotton- wool filter through the apparatus, while it was cold. At first, 
I could not succeed in getting air free from dust-; fogging always took place on 
reducing the pressure in the flask, showing that dusty air was leaking in some- 
where, and mixing with the filtered air. After much time spent in remaking 
all the joints, it was discovered that the air-pump valve was not quite tight ; 
by allowing the leakage to bubble through the water in the flask, it was found to 
be very slight, only about 2 or 3 c.cm. per minute. After this was put right, 
fogging still appeared, showing that there was still leakage. This time it was 
traced to the stop-cock between the filter and the test-flask. This leakage was 
smaller than the other, yet it let in dust. After all leakages had been stopped, 
the cotton-wool filter was removed, and the thermic filter being heated, was now 
found to do its work satisfactorily, though more slowly than a cotton- wool filter. 
The ease with which dust passes through small openings is surprising ; indeed, 
I have found that any opening which admits air, also allows these less than 
microscopic particles to pass, and yet the air in its passage through the wide 
channel of this filter had every particle of dust taken out of it by the thermal 
conditions to which it was subjected. 

If we cause the filter to purify air into which we have intentionally put a 
good deal of dust, such as dust of calcined magnesia, we find all the dust 
collected on the surface of the cold tube, near the end where the air entered, 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 263 

while the hot tube is quite clean. If we send the smoke of a cigar through the 
filter, nothing but perfectly transparent gases come out at the other end. The 
effect of coating the cold surface with glycerine has been tried, as it seemed pos- 
sible that the dust deposited on the clean surface might be carried on by the air 
current. The dust, however, seems to be firmly held on a cold clean surface, and 
no decided improvement was got by the addition of the glycerine. No accurate 
experiments have been made to determine the best size of the filtering channel. 
The filters with very narrow passages and those with much wider ones all work 
well, but no quantitative experiments have been made as to their relative values. 
It is not easy to determine what influence difference of temperature has on 
the action of a cotton- wool filter. Heating the cotton- wool has little effect in 
reducing its filtering powers. "We might expect this, as the cotton and the air 
passing through it rapidly acquire the same temperature ; and it is extremely 
difficult to say how much of the action of this filter depends on the slight 
differences of temperature produced by the air in passing through the cotton. 

Diffusion Effects. 

I shall now describe two experiments on diffusion, which were made in the 
hope they would throw some light on this repelling action of hot bodies. For this 
purpose a tube similar to those used in the previous experiments was taken, 
and an opening made in the side of it, at the front end. Into this opening was 
fitted a thin plug of plaster of paris. The surface of the plug was made flat, 
and when put in the dust-box was placed vertically, as in the experiments on 
the heat effect, to get rid of the distribution due to gravitation. This diffusion 
diaphragm was blackened, to enable the effect to be better observed, as a white 
surface reflects so much light, it makes it difficult to see what is taking place. 

After the diffusion apparatus was fitted in its place, the dust-box was filled 
with sulphate dust, and left till everything had acquired the same temperature. 
Carbonic acid gas was then introduced into the tube. At once a downward 
current was produced in front of the diaphragm, the dust particles kept 
close up to its surface, and if there was any tendency to the formation of a 
clear space the carbonic acid at once closed it. The apparatus for supplying 
the carbonic acid gas was then removed, and a small pipe connected with the 
gas pipes was then led into the diffusion tube, so as to get the effect due to the 
diffusion of gases lighter than air. The effect in this case was the opposite of 
that given by the carbonic acid. An upward current at once started, and a 
thin clear space formed in front of the diffusion diaphragm. These experiments 
prove that the dust particles move in the direction in which the greatest rate of 
diffusion takes place. This at first sight looks very self-evident; but we must 
remember that in front of the diffusion diaphragm, when hydrogen is coming 

VOL. XXXII. PART II. 2 X 






264 MR JOHN AITKEN ON THE 

through it, that the ascending clear space is not composed entirely of the lighter 
gas which has come through the diaphragm. In that clear space the larger 
proportion of the molecules are air molecules ; and while the air molecules 
advance up to and pass through the diaphragm, the dust particles are driven 
away from it. 1 shall presently have to refer to this. 

When speaking of the action of heat and moisture in protecting the lung 
surfaces from contact with the suspended dust in our atmosphere, no mention 
was made of this diffusion effect, as it can be better considered here. In our 
lungs the small quantity of tidal air, which flows backwards and forwards, 
carrying in the oxygen, and out the carbonic acid, never gets further than the 
main bronchial tubes, and does not penetrate to the air-cells ; the carbonic 
acid, set free into the residual air in these cells, is carried outwards to the tidal 
air by diffusion, and at the same time oxygen is diffused from the tidal air 
towards the residual air. Now, what is the effect of this diffusion on the 
distribution of the dust % We have seen that in diffusion through a porous 
diaphragm the dust moved towards the carbonic acid. If this was the case 
in our lungs, then the dust would tend to penetrate towards the air-cells 
and come into contact with their surfaces. In our lungs the exchange between 
the carbonic acid and the oxygen does not, however, follow the law of diffusion 
through a porous diaphragm, but those of osmose; and the rate of passage 
of these gases through the lung surfaces does not depend upon their relative 
densities, but on much more complicated conditions, of which solubility is in 
this case one of the principal. The result is, that in our lungs for every volume 
of oxygen that passes inwards, exactly or almost exactly one volume of 
carbonic acid passes outwards. These diffusion effects balance each other, and 
the result is that diffusion has no tendency to cause dust to penetrate towards 
the air-cells, or to adhere to the surfaces of our lungs. 

Repulsion due to Heat. 

We shall now consider the cause of the repulsion of the dust particles by 
hot bodies, and see if we can make out the mechanism by which the particles 
are driven away. This is a subject of considerable difficulty, and one on which 
I fear there will be much difference of opinion, and I shall simply state here 
what appears to me at present to be the cause of the particles moving away 
from a hot and towards a cold surface. The simplest explanation, and the one 
which offered itself first, was that possibly it might be a radiation effect, and 
that the particles are repelled in the same way as the vanes of a Crookes' 
radiometer by the reaction of the heated gas molecules in the way explained by 
Professors Tait and Dewae. We might suppose the side of the particles next 
the hot surface to be warmed by radiation, and the gaseous molecules on that 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 265 

side getting heated by contact, would rebound from it with greater velocity 
than those on the other side, the dust particles being thus driven away in a 
sort of rocket fashion. On examination, however, this explanation does not 
appear satisfactory ; because the particles are so very near the hot surface that 
they will not be heated principally by radiation, but by contact with the hot 
gases near the heating surface, radiation having but a slight effect. 

So far as I have been able to form a mental picture of the mechanism of 
this repulsion, it seems to be produced in the following way :— First, let us go 
back to the diffusion experiments. We saw that when hydrogen was diffused 
into air, a clear space was formed over the diffusing surface. Now why was 
this ? The air molecules were moving towards the diaphragm and passing 
through it, yet they did not carry any dust particles with them. The reason 
seems to be this. In the air in front of the diaphragm there are two currents 
of molecules — one of hydrogen, moving outwards from the diaphragm, and one 
of air, moving inwards ; but as the hydrogen current is the stronger, it carries 
the dust particles along with it, and the difference in the strength of these two 
currents in this case gives rise to a thin clear space over the diffusing surface. 

Let us now apply the same reasoning to the heat effect. When we re- 
member that hot and cold gases tend to diffuse into each other, the explanation 
given does not require to be greatly altered. The molecules of air on the surface of 
the hot body get heated by contact, and these molecules tend to diffuse themselves 
outwards into the colder molecules. In imagination, let us look at a section of 
the air close to the hot body. The air there is no longer homogeneous. Some 
of the particles have more kinetic energy than others. Those molecules with 
the greatest kinetic energy have the greatest amount of their motion in a direc- 
tion away from the hot surface, while the cold ones have the greater amount of 
their motion in a direction towards the hot surface. Now what will happen to 
any particle of matter hung among these heterogeneous molecules ? The side of 
the particle next the hot body will be bombarded by a larger proportion of hot 
molecules than the other side, and the result will be to drive the particle away 
from the hot body. It maybe objected that, as the air pressure is the same on 
the front and back of the particles, therefore the total energy of the molecules on 
the front and on the back must be the same, and therefore there will be no 
tendency to cause the particles to move. I think, however, this does not cor- 
rectly represent the case. Near the heating surface the hot molecules are 
moving outwards and the cold ones inwards. If there were more cold ones 
moving inwards than hot ones outwards, so that the total energy of the inward 
moving ones was equal to the total energy of the outward moving ones, which 
would be necessary in order that the pressures might be equal, then no motion 
would be produced in the dust particles. We must, however, remember that 
there are exactly the same number of molecules moving each way. One effect 



266 MR JOHN AITKEN ON THE 

of the hot surface seems to be to differentiate the movements of the molecules, 
causing the greater amount of the movement of the hot ones to be outward 
and of the cold ones inward, and the outward moving molecules, having the 
greater kinetic energy, exert a greater pressure on the dust particles and drive 
them outwards. In the hydrogen diffusion effect the particles of dust were 
driven away, because a greater number of hydrogen molecules were moving one 
way than air ones the other. In the heat effect they are driven away, because 
the molecules moving from the hot surface have a greater kinetic energy than 
those moving towards it, and the particles are bombarded on the one side by a 
greater number of hot molecules than on the other. 

We have the same effect intensified when the hot surface is wet. When 
this is the case, the vapour molecules diffusing outwards carry with them the 
dust particles to a much greater distance than the heat alone, as there is no 
inward current of vapour molecules to contend with the outward one, and tending 
to drive the dust particles inward ; the result is, we get a dark plane at 
least twice as thick with heat and vapour as with heat alone. Of the two, the 
vapour seems to be the more powerful, as very little heat with moisture gives a 
thicker dark plane than double the heat would do. If we carefully fix the 
experimental test surface in a vertical position and simply wet it, the effect is 
to cool it by evaporation, and a downward current is produced ; but, at the 
same time, a clear space is formed, showing that in this case the outward 
effect of the vapour is greater than the inward effect of the cold. 

There seemed to be a possibility of getting an answer by experiment as to 
whether the radiation or the diffusion theory is the correct one. If radiation is 
the cause of the repulsion, then we should expect that a good radiator would 
cause the particles to be driven further away, and thus cause a thicker dark 
plane than a bad radiator. For the purpose of testing this, another experi- 
mental flat test-surface was prepared. This test-surface was made of silver and 
highly polished. One-half of it was then covered with lamp-black. After the 
test-surface was fixed in the dust-box heat was applied to it, and the thickness 
of the clear space over the two halves of the test-surface carefully noted. To 
do this, the dust-box was so arranged that I could look down the test-surface — 
not across it as usual — and could thus see down the boundary line between the 
dark plane over the polished surface and over the lamp-black. The result was, 
not the slightest difference could be detected between the two. The boundary 
line of the dark space in front of the plate was a straight line parallel to the 
surface of the plate. This experiment, while it gives no support to the diffusion 
theory, shows us that radiation is not the principal cause of the dark plane. 

If the explanation here given of the repulsion of the dust by a hot surface is 
correct, then this effect is not produced in the same way as the repulsion of the 
discs of a Crookes' radiometer when heat is falling on them, but is similar to 



FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 267 

the repulsion of the discs by a hot surface placed inside the radiometer bulb, as 
in the apparatus described by Mr Crookes in Nature, vol. xv. p. 301. In this 
radiometer the vanes were made of very clear mica, and they did not rotate 
when light fell on them. Inside the bulb, and just clear of the discs, was fixed 
in a vertical plane a blackened plate of mica. When the light was allowed to 
fall on this fixed and black plate, the vanes instantly rotated as if a wind were 
issuing from this surface. The energy which causes the repulsion of the dust 
and of the discs of this radiometer is transferred in both cases from the 
hot surface to the repelled surface by the kinetic energy of the gas molecules, 
and not by radiation. 

Another consideration which indicates that the force causing the movement 
of the dust is not transferred by radiation is the well-known fact that radiant 
heat is not much intercepted by dust. When we concentrate a strong beam of 
light and heat in dusty air by means of a lens, perhaps one of the things which 
strikes us most is the very slight heating effect which is developed at the focus. 
The dust is not destroyed, and no rapid upward current is formed. But if we 
place a piece of paper at the same focus it is at once charred, and a rapid 
current of air rises from its heated surface. 

The rate at which vapour molecules diffuse under the conditions existing 
in the experiments is very great, and seems to be quite sufficient to account for 
the results. Take, for instance, the water molecules when they pass into 
vapour. Vapour molecules are selected because we can follow their move- 
ments. In a small fraction of a second they diffuse to a distance of nearly 
1 cm. This can be seen in the experiment described with the flat test-surface 
when moistened. With a slight rise of temperature, fog particles are seen 
forming in the current, rising in front of the wet surface. Even at the lower 
edge of the plate these particles are seen at some distance from the plate, and 
separated from it by a dark space, showing that even at that point the 
vapour molecules have already diffused outwards to a distance and far beyond 
the dark space, while probably other molecules have gone further than the fog 
boundary, but are under conditions which keep them in the state of vapour. 

Or take the reverse of this diffusion process, seen in the evaporation of fog 
particles. Let us blow some steam into the dust-box, so as to form a regular 
fog, but without adding any dust. Into this fog introduce a piece of very 
dry wood ; if it is charred so much the better, as its blackness enables us to see 
more easily what is taking place. It will be observed that there is formed all 
round the wood a clear space, in which not a particle of fog can be seen. If 
we watch the air currents we shall see the particles approaching, but vanishing 
at some distance from the wood, and over the wood the particles will be seen 
falling into the clear space and disappearing. This clear space is caused by 
the wood absorbing the vapour in the air near it, thus surrounding itself with 



268 MR JOHN AITKEN ON THE 

a space of dry air, into which the fog particles evaporate as they approach, and 
so rapid is the diffusion towards the wood that the air is kept dry enough to 
evaporate the particles as quickly as they approach. 

Attraction Due to Cold. 

To explain the attraction of the dust particles by cold surfaces, we have only 
to reverse the explanation given of the repulsion due to heat. At the cold sur- 
face the outward moving molecules of air have less kinetic energy than the 
warmer inward moving ones, and the dust is thus driven towards the cold 
surface by the greater energy of the hot molecules. 

This explanation of the action of hot and cold surfaces may not at first 
sight seem satisfactorily to account for the peculiar movements of the dust 
particles as they approached the hot wire, in the experiment shown in fig. 13. 
We might here ask ourselves, for instance, Why were some of the particles 
carried close to the wire, and then driven away from it % The inertia of 
the particles is clearly not sufficient to cause them to advance against the force 
which produced their rapid repulsion. Then why did they approach so close 
to the wire, and then appear driven away with such violence ? It looks as if 
the particles had become heated to a temperature sufficient to drive off their 
occluded gases and condensed vapours, and that the repulsion in this case was 
due to the rapid escape of these gases and vapours. No doubt, something 
will be due to their escape, but I do not think it is the principal cause of the 
repulsion, because the particles are so small, the gases and vapours will escape 
from their surfaces all round them, and their effects will therefore nearly balance. 
Further, the escape of these gases will not explain why the particles were 
always driven towards cold surfaces. The following seems to be the principal 
reason why the particles are always driven sideways and not downwards. The 
rate at which a particle of dust will be repelled from the surface of a body is 
not necessarily the same in all directions round the body, but will depend on 
the closeness of the isothermal lines at the different places; and as in the experi- 
ment the temperature varies very much more rapidly towards the cold glass 
at the sides than it does downwards, the result is, a more powerful impulse is 
given sideways than downwards; and further, the cold glass surfaces diffe- 
rentiate the molecular movements near them, and cause an attraction. 

Let me illustrate this point further, and show by a parallel case in the action 
of gravitation, why it is that the particles of dust when repelled move towards 
the side, and not downwards. Suppose there is a very long, but narrow and 
regularly shaped mountain, with its highest point near the middle, and the sides 
sloping regularly and quickly to the summit, while the ridge descends slowly. 
In ascending such a mountain, we can either go up the long easy slope of the 



FORMATION OF SMALL CLEAR SPACTS IN DUSTY AIR. 269 

ridge, or up the steep sides. Now, suppose a stone to be rolled up the 
ridge of this mountain, by a force acting in a direction along the ridge, 
it is evident that if the stone gets off the ridge, that it will fall down the 
quicker slope towards the side ; and if the stone keeps the ridge, and we 
succeed in rolling it nearly to the summit, but there meet a slope too steep 
for us to push the stone up, then the stone will obviously be in a position of 
unstable equilibrium, and the slightest fall will cause it to leave the easy slope 
of the ridge, and, once started on the quick descent of the sides, its motion will 
be rapidly accelerated in a direction at right angles to that in which we are 
pushing ; thus the stone will descend the quick slope of the side with great 
velocity, even while the force which pushed it up the ridge is still acting on it. 
The direction in which the force now acts on the stone is such that it no longer 
tends to prevent it falling ; and further, supposing it was directly opposed to 
its motion, it would have but little effect against the steep slope of the 
side. Now draw the contour lines of this mountain. It will be found that 
they exactly correspond to the isothermal lines round the hot wire placed 
between the cold plates. The dust and the stone each fall towards the side, 
because that is the direction of steepest slope. 

General Remarks. 

This tendency which the dust in our atmosphere has to move away from 
hot bodies, and attach itself to cold ones, will, I have no doubt, help to explain 
many phenomena which are not at present well understood. No doubt, many 
things will suggest themselves to different minds as receiving their explanation 
in this somewhat curious liking of dust for lodging in cold places. Among 
other things, it explains the reason why stove and hot-air heated rooms are 
always so much dirtier than those warmed by open fires. In a stove-heated room 
the air is warmer than the walls and than the objects in the room, the dust there- 
fore tends to leave the air, and to deposit itself on every object colder than 
itself in the room ; whereas, in a room warmed with an open fire, the heating 
being principally done by radiation, the walls and furniture are hotter than the 
air, they therefore tend to throw off the dust, and eveu when it does fall on them, 
it does not adhere with that firmness with which it does to a cold surface, and 
any breath of air easily removes it. 

Diffusion also, no doubt, plays some part in determining whether dust 
shall or shall not adhere to the walls and ceilings of rooms. 

Again, a knowledge of this tendency of dust to settle on cold surfaces is 
necessary to enable us fully to explain why so much soot adheres to the inside 
surfaces of chimneys. If the smoke were cold, so much soot would not settle in 
the chimneys, nor would it adhere so firmly. 

A simple experiment to illustrate this tendency of dust to leave warm, and 



270 MR JOHN AITKEN ON THE 

to settle on cold surfaces, is made in the following way : — Take two narrow 
strips of glass mirror, any substance will do, but the mirror surface shows the 
result best. Arrange so as to hold these strips of glass face to face, and with 
their surfaces at a distance of a few millimetres, but before putting them in 
their places, heat one of them to a temperature of say 100° C. Have ready 
a tall glass vessel, large enough for the glass strips to enter freely. Now 
fill this vessel with some dust, by burning sodium or magnesium, or by shaking 
up some calcined magnesia or other powder. By the time the air in the vessel 
is settled and cooled, but before the dust settles, have ready the glass strips, 
one of them hot as directed, and placed in front of the other, face to face, 
with an air space between. Now put the mirrors into the vessel among the 
dust. After a minute or so examine them. The following will be the result. 
The hot one will be quite clean, while the cold one will be white with dust. 
That the dust has no tendency to settle on the cold one, may be proved by 
putting at the same time in the vessel another cold strip some distance from the 
hot one, when it will be seen that this one is almost entirely free from dust, 
depending upon whether it was a little hotter or colder than the dusty air. 

When one looks at the enormous amount of dust deposited on the cold 
mirror in this experiment, we cannot help associating the result in some way 
with the condensation of vapours, and it takes some time before we can arrange 
our ideas and realise that the thick white deposit was truly thrown out of 
suspension and settled on the mirror in the solid state, and was not in the state 
of vapour before coming into contact with the cold glass. 

A somewhat curious experiment may be made with light calcined magnesia 
powder, which shows the action of this force in a marked way. The magnesia 
is heated to a good red heat in an iron vessel. If we now take a metal 
rod 5 or 10 mm. diameter and heat it as hot as the powder. We may then 
dip in into the powder, and stir it as much as we please, but on taking the rod 
out, it will be found to be quite clean. But if the rod is cold, it comes 
out of the powder with a club-shaped mass of magnesia adhering to it, 
so thick that the magnesia-coated end is twice as thick as the rod itself. 
If the rod is kept in the hot powder for a short time, and then taken out, 
with its coating of powder adhering to it, whenever the powder gets outside 
the hot vessel, and exposed to the cold, it falls away, as the inside of the 
powder is now hotter than the outside. 

Most of us have noticed when heating powders, particularly if they are 
light, that while they are heating they take on a peculiar semi-fluid appear- 
ance if stirred, or if the vessel is tilted back and forwards. This I have 
always supposed was due to the escape of occluded gases from the powder, 
keeping it in a state of semi-suspension. Now, however, I think this peculiar 
effect is a result of the repulsion due to heating. My reason for supposing this 






FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 271 

is, that if after the powder is heated it is cooled quickly, and again heated 
before there is time for it to absorb gases, the same semi-fluid appearance 
is again produced while heating. Further, if the powder, instead of being 
heated in a closed vessel,, is placed in a cup, so that the under side of 
the powder is kept hot, while the top is cooled by radiation, so long as 
these conditions are kept up the powder retains its fluid-like properties, 
moving about on the slightest tilting of the cup, and conducting itself in a way 
very suggestive of the spheroidal condition, but without any generation of 
vapour to give rise to the irregular movements seen in liquids. It seems 
possible that something of the spheroidal condition may receive its explanation 
in this repulsion between hot and cold surfaces. This repulsion may be illus- 
trated by placing a hot and a cold surface together. A piece of cold glass, for 
instance, slides about in a remarkably easy way on a hot surface of glass. 

Many practical applications of this attraction and repulsion will no doubt 
be found. It might be easily applied to the condensation of those fumes from 
chemical works which at present are allowed to pollute the air. But perhaps 
the application of most general interest would be towards the prevention of 
smoke, or rather the prevention of the escape of smoke into the atmosphere. 
Whatever interest, however, it may have in this way, it is clear it can never 
meet with general adoption, save under compulsion, as it will effect no saving 
in fuel, such as would result from more perfect forms of combustion. 

I have, however, made some experiments in this direction, and find that by 
placing a tall metal chimney over a very smoky paraffin lamp, surrounding 
this chimney with another tube slightly larger, and causing the products of 
combustion to rise up the centre tube, and descend through the annular 
space between the two tubes, the soot is all taken out, and nothing but a white 
vapour is see a escaping. On examining the tubes after they have been in use 
some time, the inside surface of the inner one is found to be slightly coated 
with soot, while its outer surface is perfectly clean and bright, not a speck of 
dust on it, and the inside of the outer tube, which is only a short distance from 
it, is thickly coated with soot. This arrangement, however, is too complicated, 
save for special purposes. 

It has been already stated that the reason why so much soot collects in 
chimneys is that the gases are hotter than the sides of the chimney. In cases 
where the gases are allowed to escape at a high temperature advantage might 
be taken of this tendency. If we simply cooled the smoke in the presence of 
plenty of depositing surface, much of its soot would be trapped out, and the 
escaping smoke made less dense. The amount that might be trapped in this 
way will depend on the extent to which the gases could be cooled. 

For works with large chimneys this plan evidently could not be adopted, 
and in their case the purification would require to be down at the bottom of the 

VOL. XXXII. PAET II. 2 Y 



•27 '2 MB JOHN AITKEN ON CLEAR SPACES IN DUSTY AIR. 

chimney. The evident objection to this is, that as the gases are cooled in the 
depositer, the draught in the chimney will be destroyed. This, however, can 
be avoided by the use of "regenerators." The impure air would be led to a 
cold regenerator, where it would be cooled and its impurities deposited; and 
when purified it would be led through another chamber, where it would be heated 
before being sent up the chimney. This arrangement would not require heat to 
be spent in working it, as the process would be reversed, and by simply revers- 
ing the direction of currents from time to time the heat stored up in cooling 
would be used for heating the purified gases before being sent up the chimney. 
This purifying process by heating and cooling would require to be done a 
number of times, and the air sent through a succession of regenerators before it 
could be made perfectly pure. 



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( 273 ) 



XVI. — On Stichocotyle Nephropis, a new Trematode. By J. T. Cunningham, 
B.A., Fellow of University College, Oxford, and Naturalist in charge of 
the Marine Station, Granton, Edinburgh. (Plate XXXIX.) 

Z. (Read 5th May 1884.) 

The Norway lobster, Nephrops norvegieus, on account of its abundance in 
the Firth of Forth, and the consequent ease with which it can be obtained from 
the Newhaven market, is given to the practical classes in the Natural History 
Laboratory of Edinburgh University for dissection, as an example of the de- 
capoclous Crustacea. One day in December last, while I was superintending 
the work of a class engaged in the study of this animal, one of the students, 
whose name I have unfortunately forgotten, called my attention to some glob- 
ular protuberances on the intestine of the specimen he was dissecting. At the 
time I was unable to answer his questions any further than to say that the 
protuberances were the cysts of a parasite, and I put the specimen by for sub- 
sequent examination. On opening the cysts afterwards I found in them a 
small white worm, which proved to be a Trematode possessing novel charac- 
teristics. In the following paper I shall describe this parasite, and show that 
it is so distinct from all Trematodes hitherto known as to constitute a new 
genus. On several occasions I had the pleasure of examining the animal in 
the company of my friend and former colleague, Mr Duncan Matthews, and 
some of the points in its structure were first noticed by him. 

I will first describe the animal as completely as possible, and then deal with 
the manner of its occurrence and its relation to other Trematodes. 

The worms when taken out of the cysts are elongated and cylindrical in 
shape, one surface, the ventral, being slightly flattened; they vary in length 
from 75 mm. to 8*0 mm. They are white in colour and somewhat opaque, so 
that there is considerable difficulty in making out their internal anatomy under 
the microscope. The body tapers towards each end, the thickest part being 
near to the oral or anterior extremity. The arrangement of the organs is bi- 
laterally symmetrical. The mouth is a small simple circular aperture, situated 
on the ventral surface, close to the anterior end of the body. Behind it, 
: along the median line of the ventral surface, is a single row of large muscular 
, suckers, which diminish gradually in size towards the posterior end. The 
i margins of the mouth are muscular, and its cavity can be dilated and con- 
tracted, so as to act as an additional sucker. When the animal is viewed with 
its ventral surface upwards, slightly compressed by a cover-glass, and under a 

VOL. XXXII. PART II. 2 Z 



274 MR J. T. CUNNINGHAM ON 

low power, it presents the appearance shown in Plate XXXIX. fig. 1. The 
ventral series of suckers is seen along the median line ; each of them has a 
central depression varying in size according to the state of contraction, and 
round this is the projecting rim, in which can be seen the radiating muscles by 
which the sucker is dilated. The number of suckers present varies in different 
individuals according to their age and size, — the smallest specimens, such as the 
one shown in fig. 4, may have as few as 7, the larger usually have 15 or 16, 
while in the largest I have counted as many as 22. No doubt specimens 
might be found the totals of whose suckers would supply all the intermediate 
numbers between these. 

The suckers are always more difficult to distinguish at the posterior end of 
the series, where they are very small, and they evidently increase in number 
at this end, just as the segments of a Chaltopod. It is this approach to meta- 
merism which renders the creature specially interesting. The metamerism, 
however, does not extend to any of the other organ systems, and consequently 
the animal cannot claim among the Trematodes so isolated a position as the 
Gunda segmentate/,, described by Lang, among the Turbellarians. From the 
disposition of the system of suckers, I have named the animal Stichocotyle, 
adding Nephropis for the specific name, from the name of its host. 

The surface of the body is marked by closely set transverse folds, which are 
indicated in fig. 1, between the suckers. These folds, seen in optical section, 
give the body a crenated outline, which is also indicated in the figure. When 
the body is much extended, either by compression or by the muscular move- 
ments of the animal, the folds disappear ; they are probably due to the pre- 
sence of an inelastic cuticle, although neither in the opticle nor actual section 
of the integument can a separation between cuticle and epidermis be dis- 
tinguished. The external layer of the body wall, as seen in optical section 
in the living animal, is homogeneous and transparent, and of considerable 
thickness. 

The most conspicuous of the internal organs are the main canals of the 
water-vessel, or excretory, system. These are two in number, one running 
down each side of the body through its whole length. Their size, in compari- 
son with that of the whole animal, is extremely large ; their walls are thrown 
into transverse folds. The interior of the canals is crowded with large spherical 
concretions similar to those found in the excretory system of other Trematodes 
and of Cestodes. These concretions, during the examination of the living 
animal, are continually moving with considerable rapidity, the contractions of 
the body forcing them suddenly from one part of the canal to another. In the 
middle line, between the main excretory canals, is the intestine. From the 
mouth can be traced a narrow oesophagus, dilating into a muscular pharynx, 
with thick walls, and this leads into an intestine which diminishes slightly in 



STICHOCOTYLE NEPHROPIS, A NEW TREMATODE. 275 

diameter towards the posterior end, where it ends blindly. The intestine is 
quite simple, and has no branches or diverticula. 

When a specimen is examined with its dorsal side upwards, and consider- 
ably compressed, the intestine and lateral excretory canals are seen with great 
distinctness, as there are no muscular thickenings dorsally to form suckers. 
Fig. 2 shows somewhat diagrammatically the view thus obtained. At the pos- 
terior end the two lateral canals terminate in muscular portions, which pass in- 
wards behind the intestine, and unite to form a single median chamber with thick 
muscular walls. This chamber opens in the usual way by a pore on the dorsal 
surface, close to the end of the body. The rhythmical dilatation and contrac- 
tion of the terminal chamber is very pronounced, and it commonly happens, 
when the animal is under compression, that one of the spherical bodies con- 
tained in the lateral canals passes into the terminal chamber, and is expelled 
from the dorsal pore with some force. The appearance of the terminal part of 
the excretory system under a high power is shown in fig. 3. 

When the living animal is very attentively examined with an objective of 
high power, by careful focussing fine ciliated canals can be made out be- 
tween the large lateral canals and the dorsal surface. It is probable that, like 
the corresponding fine canals in other Trematodes, these open into the main 
lateral canals, and are, on the other hand, in communication with the inter- 
cellular spaces of the body-parenchyma; but owing to the opacity of the 
tissues, I have not yet succeeded in tracing out these relations. The cilia, whose 
motion alone enables one to trace the tubules in question, are of great length, 
and are situated on the walls of the tubules at intervals. I have not been able 
to discover any " entonnoirs cilids " at the ends of the branches of the system 
of tubules, like those described by Fraipont.* I have followed the ciliated 
tubules sometimes for considerable distances. Their course is somewhat irre- 
gular, but maintains a longitudinal direction. They branch occasionally, but 
the branches never extend into the median region of the body above the intes- 
tine. I have not found any tubules on the ventral side of the body, but they 
extend forwards beyond the anterior limit of the main lateral canals. 

I have now described the general disposition of the digestive, excretory, 
and integumentary systems of the animal, and have hitherto mentioned nothing 
which cannot be made out in living specimens. No reference has been made 
to the generative or nervous systems. In the stage of the animal's history 
which is passed within the body of Nephrops neither of these systems is 
developed. I shall refer to structures which may be their rudiments. Special 
sense organs are altogether absent. 

In order to examine the histological structure of the tissues, I have pre- 

* " Reck sur l'appareil excreteur des Tr£in. et Cestoides," Julien Fraipont, Arc. de BioJogie, Tom. i. 
1880. 



276 MR J. T. CUNNINGHAM ON 

pared transverse sections in continuous series from specimens preserved with 
picro-sulphuric acid, and stained with borax-carmine. The specimens chosen 
for this purpose were of the medium size, carrying about 16 suckers. The 
sections are all very similar to one another, differing chiefly in the relation 
which they bear to the series of suckers. In one taken from the middle of the 
series, the intestine is seen in the centre, elliptical in outline, the long axis of 
the ellipse being dorso-ventral. The epithelium of the intestine is thick, and 
composed of large nucleated cells, which form sometimes more than one layer, 
and are not quite regular in arrangement. Both in the living animal and the 
prepared section it can be seen that the cells of the intestinal epithelium are 
rapidly proliferating ; the free ends of the cells project into the lumen in various 
degrees, and a number of detached cells are seen lying free in the interior. 
In the living animal these cells float about under the influence of the move- 
ments of the body, and are occasionally expelled from the mouth. Some of 
them contain minute round granules. 

On each side of the intestine is the section of one of the main lateral 
excretory canals, in which there is no distinct epithelium to be seen. There 
are nuclei in the walls, and the cavity may be lined by an epithelium of ex- 
tremely thin cells, to which these nuclei belong. The walls of the canal are 
extremely thin. 

The parenchyma of the body, or mesenchyma, appears in the sections as a 
fine reticulum with deeply stained nuclei at the nodes. The actual structure of 
the mesenchyma in Trematocles has been much disputed,"" some observers 
maintaining that the intercellular spaces are globular and the cells stellate ; 
others, vice versa, that the cells are globular, and the intercellular spaces reticu- 
late. In the living Stichocotyle the mesenchyma is seen to be crowded with 
minute bright refringent granules, which seem to be contained in intercellular 
spaces, as they move through considerable distances in parts of the animal 
Avhich are in active contraction. They are shown in fig. 3. 

The muscular layers of the body wall are imperfectly differentiated ; they 
arc represented by a zone of closely crowded nuclei at the periphery of the 
mesenchyma, and, external to this, a zone of small dots, which are probably 
the sections of longitudinal fibrils. The account of the muscular layers of the 
integument in the young of Amphilina, given by SALENSKY,t agrees pretty 
closely with the state of things in my sections, except that he mentions nuclei 
in the external of the two layers, and in the zone of dots I have described 
there are no nuclei. 

The sucker is composed chiefly of elongated cells, whose long axis is per- 
pendicular to the epidermis. These are simple muscular cells which dilate the 

* Vide Fraipont, loe. cit., p. 428. 
f Zeit. f. tvis. Zool, Bd. xxiv., 1874. 




STICHOCOTYLE NEPHROPIS, A NEW TREMATODE. 277 

cavity of the sucker. Nuclei are scattered through the tissue, each cell pro- 
bably possessing one. The muscles which contract the cavity of the sucker are 
not so conspicuous. The tissue of the sucker is separated from the tissues of 
the body by a thin limiting membrane, which is continuous at its periphery 
with the limiting membrane of the epidermis. This is an arrangement which 
is not easily explained, as, the muscles of the sucker being probably a special- 
isation of the ordinary muscles of the body wall, it would be expected that the 
continuity between the two would be maintained. 

Beneath the lateral excretory canal of the right side, in the anterior sec- 
tions, is an area occupied by very closely crowded nuclei. This can be traced 
through successive sections of the series as far as the end of the fifth sucker. 
It passes from its first position, under the right main canal, to the left side of 
the same canal, at the same time becoming thicker, and towards its termination 
becomes so broad as to extend beneath the intestine from the right canal to the 
left. There is thus an irregular cord of small unmodified cells extending 
through a considerable part of the length of the body, and it is possible that the 
generative organs of the adult are derived from this. 

The most external layer of the body representing the epidermis and cuticle, 
is in sections, as in the living animal, quite homogeneous. I have not yet been 
able to distinguish in it either nuclei or cell boundaries, or a separation between 
epidermis and cuticle. The layer becomes thinner where it lines the cavity of 
the sucker. In the living animal small funnel-shaped openings are seen in the 
epidermis, which may be the apertures of glands, but as they are not visible 
in the sections it is possible that they are only fractures produced by com- 
pression. 

The only trace of tissue which may belong to the nervous system is a tract 
composed of very fine fibrils in some of the sections anterior to the mouth. 
This tract forms a band extending horizontally across the body near to the 
dorsal side. The fibrils of which it is composed are extremely minute, and the 
whole tract is destitute of nuclei. It is shown in fig. 6, and may represent the 
cerebral ganglion. A pair of processes from this mass of tissue can be traced 
through the succeeding two or three sections, which are probably the rudiments 
of a pair of lateral nerve-cords. They pass downwards towards the under side 
of the main excretory canals. 

The cysts in which the animal occurs are scattered on the extremely thin 
walls of the posterior part of the intestine of Nephrops, in the region of the 
abdomen. They sometimes contain more than one worm, as many as six 
having been taken by Mr Matthews on one occasion from a single cyst. 
Usually the wall of the cyst is soft and opaque, and white or light yellow in 
colour. It is of a cellular nature, and is apparently a pathological product of 
the tissue of the intestine of the host. 



278 MR J. T. CUNNINGHAM ON 

The cysts vary in size with the age and size of the worm within, and the 
youngest and smallest ones are brittle and dark brown in colour. A very 
young worm taken from such a cyst is shown in fig. 4. It has only seven 
suckers. The worm in all cases, when placed on a slide in a little water, 
exhibits movements of contraction and extension, and coils or straightens its 
body, but is not able to travel over much space. When an infected crayfish is 
opened which has been twenty-four hours out of water, the worms are often 
found to have escaped from the cyst, and are found lying on the muscles ; but 
I think this does not take place while the Nephrops is living. The number of 
c}*sts varies considerably. I have sometimes found them covering the posterior 
part of the intestine completely; and in other cases only two or three of the 
very smallest brown cysts were present. The diameter of the cysts varies from 
•5 mm. to 2 or 3 mm. I have taken as many as forty worms from a single 
Nephrops. 

The proportion of specimens of Nephrops infected is not small. In one 
case I found three out of eight contained the parasite. Usually out of a dozen 
opened three or four are infected ; but sometimes a dozen may be searched 
without a single parasite being found. My observations have extended now 
over nearly four months, and I have not yet found any variations in the state of 
the parasite. 

I have not found the parasite in any other part of the body of Nephrops 
except the intestine ; and I have no evidence to show whence it is derived, 
what is its mature state, or in what conditions its adult stage is passed. 

It seems probable that the eggs are taken into the stomach of Nephrops 
with its food, and that an embryo escapes from the egg, which pierces the wall 
of the intestine, and there develops into the stage of the worm which I have 
examined. The further development most likely takes place in the body of 
some large fish which feeds on Nephrops ; but hitherto no Trematode is known 
living inside the body of a marine fish except the Calicotyle Kroyeri, which is 
found in the cloaca of rays, and Encotyttabe Pagelli in the mouth of Pagelhis 
centrodontus* 

In passing on to consider the affinities of the parasite, it may be set down 
as obvious that it is in every respect a typical Trematode. The characters of 
the water-vessel system and of the suckers could not be found outside that 
class. But the arrangement of the suckers is entirely novel. A serial arrange- 
ment of the suckers is not uncommon among Trematodes ; but there is no 
other genus in which they form a single series extending along the median 
ventral line through nearly the whole length of the body. The series when 
present is usually double. Microcotyle t has in the posterior third of its body 

* Van Beneden et Hesse, Mem. Acad. Boy. de Belg., Torn, xxxiv. 
t Ibid. 



STICHOCOTYLE NEPHROPIS, A NEW TREMATODE. 279 

a series of small suckers on each side. They are very numerous, and all of the 
same size. In Octocotyle * there are, near the aboral extremity, four pairs of 
lateral suckers, one pair behind the other. The suckers of Gastrocotyle t form 
a single series along the edge of a projecting membrane on the right side of the 
body. Ernst Zellek describes a serial repetition of pairs of suckers as an 
occasional abnormality in Diporpa. j At the posterior extremity of this genus 
there is a pair of large suckers forming divergent projections. Zeller met 
with a specimen in which the single pair was replaced by three pairs, one 
behind the other. In all these cases the suckers are provided with chitinous 
hooks, as in nearly all the Polystomidae. Stichocotyle is without chitinous 
armatures in any part of its body. Until the adult form is found and its 
anatomy examined, it is impossible to say anything more definite about the 
position of Stichocotyle than that it belongs to the Polystomidae, though it 
differs from all other Polystomidae in passing through an encysted stage within 
the body of another animal. 

I hope before long to trace out the whole life history of this interesting 
form, as at the Granton Marine Station I shall have good opportunities for 
carrying on the search after its earlier and later stages. In concluding the 
present account I have to express my warmest thanks to Dr Arnold Lang, of 
the Naples Zoological Station, who kindly sent me some valuable suggestions 
and references. 



EXPLANATION OE PLATE XXXIX. 

Letters of Reference. 

his. Cord of blastema. 

ci. ca. Ciliated tubules of water-vessel system. 

co. Spherical concretions in lateral canals. 

ep. Epidermis and cuticle. 

e. ap. External aperture of water-vessel system. 

/. ce. Free cells in lumen of intestine. 

;//. Openings of dermal glands (?). 

int. Intestine. 

int. ep. Epithelium of intestine. 

I. ca. Lateral canals of water- vessel system. 

me. Mesenchyma. 

mu. su. Muscles of sucker. 

m. Mouth. 

me. gr. Granules in mesenchyma. 

ne. Cerebral ganglion. 

ph. Pharynx. 

su. Series of suckers. 

te% ch. Terminal chamber of water-vessel system. 

* Van Beneden et Hesse, Mem. Acad. Roy. de Belg., Tom. xxxiv. 

f Ibid. 

% Zeits. f. wiss. Zool., 13 d. xxii. 1872. 



280 MR J. T. CUNNINGHAM ON STICHOCOTYLE NEPHROPIS. 

Figs. 1, 2, 3, 4 were drawn from fresh specimens. All were drawn without the aid of a camera 
lucida. 

Fig. 1. Ventral view of Stichocotyle, as seen under slight pressure. 

Fig. 2. Optical section of the whole animal, seen with dorsal surface upwards. 

Fig. 3. Optical section, showing termination of water-vessel system. 

Fig. 4. Very young specimen, with seven suckers. 

Fig. 5. Transverse section, passing through middle of first sucker of moderate-sized specimen. 

Fig. 6. Section through pre-oral region of same specimen. 

The fractions represent the relation of the diameter of the drawing to that of the object. 






wis. Roy. Soc.Edm r 



Ity.I. 




ep 



Vol. XXXII, PI. XXXIX. 



p?i> 



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LtKEJinf 



( 281 ) 



XVII. — The Enumeration, Description, and Construction of Knots of Fewer 
than Ten Crossings. By Kev. Thomas P. Kirkman, M.A., F.R.S. (Plates 
XL.-XLIII.) 

(Eead June 2, 1884) 

1. By a knot of n crossings, I understand a reticulation of any number of 
meshes of two or more edges, whose summits, all tessaraces (a/07), are each a 
single crossing, as when you cross your forefingers straight or slightly curved, 
so as not to link them, and such meshes that every thread is either seen, when 
the projection of the knot with its n crossings and no more is drawn in double 
lines, or conceived by the reader of its course when drawn in single line, to 
pass alternately under and over the threads to which it comes at successive 
crossings. 

The rule for reading such a reticulation of single lines meeting in tessaraces 
only is this — Coining by the edge or thread pq to the tessarace q, you leave it 
by the edge of q which makes no angle with pq, nor is part of thread under or 
over which you pass at q. 

2. It is not necessary, after what Professor Tait has written on knots, to 
prove that every reticulation having only tessarace summits, whether polyedron* 
or not, if it be one continuous figure and projected to show all its crossings and 
no more, can be read all through by this alternate under and over, so that all 
its closed circles, one or more, can be written down in numbered summits, and 
that the knot can be labelled as unifilar, bifilar, or trifilar, &c. 

3. If a thread a of a knot, after passing under or over a thread b, passes 
over or under b before it meets a third thread c, there is a linkage of two cross- 
ings and a flap between them. This flap is the small eyelet seen between two 
links of a slack chain as it lies on the table : it is a 2-gon, a mesh of two edges 
and of two crossings. Here see art. 9. 

4. In our enumeration of knots of n crossings, two, C and C, are counted 
as the same one, whenever and only when, in the number, polygonal rank, and 
order of their meshes C is either the exact repetition or the mirrored 
image of C; and I consider the threads of all the circles of a knot to be tape 
untwisted. 

5. Nothing general seems to have been written upon knots of more than 
seven crossings. Nor, fortunately for the claims of those knots upon the inte- 

* I hope to be pardoned for omitting the h. It annoys me to hear the learned say polyhedron. 
Why not periliodic also 1 or, more learnedly, perihodic ? 

VOL. XXXII. PART II. 3 A 



282 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

rested attention of the student, has unanimity been even so far secured. In 
what Listing and Tait have contributed to this theory, there is an affirmation 
of identity, or of equivalence, denoted by the symbol = , between two knots of 
seven crossings which, by the above definition of sameness, are as unlike as 
they can be. This, of course, is due to a mere difference in definitions. The 
right definition in the view of Listing and Tait I find not easy to seize, and 1 
cannot work on reticulations between equivalence and identity, nor pause to 
consider the deformations of a knot A into an equivalent knot B that can be 
effected by twisting the tape of A. I content myself by exhausting the forms 
that differ according to my definition; and I leave to a more competent hand 
the reductions to be made by twisting. 

6. The reader will judge for himself whether the number of different unifilar 
knots of seven crossings is twelve, as I am compelled to believe, or at 
most eight, as Tait prefers to say. Whatever be the decision of the reader, 
I am highly delighted, while attempting to write on a theme so dry and tire- 
some, that we have, at the outset, such a pretty little quarrel as it stands 
wherewith to allure his attention. 

7. Every polyedron which is an w-acron having only tessarace summits is a 
solid knot of n crossings, on which is neither linkage nor flap. Such a knot 
can be projected on any of its triangular or m-gonal faces, so as to show all its 
n crossings, and no more, within that face or at its summits. It has no linear 
section, i.e., no plane can cut it in space, nor can any closed curve be drawn 
upon lines of its projection, without meeting it in more than two points, on edge 
or at crossing. 

In a knot which is no polyedron, we call a section that meets it in only two 
projected summits or crossings, linear, as passing through two points only of 
the figure ; although no crossing of a mesh in space can be cut through its 
opposite angles without making four ends. 

8. No projected knot, solid or unsolid, can have a linear section through 
one edge kl only, and through one crossing q only. For, if it can, let the two 
threads at q on the left hand of the section be pq and rq, pq passing over rq at 
q ; then ji><7 at the crossings passed under a thread, and rq at r passed over one. 
Cut at q, making four ends ; reunite into one thread rp the two ends on the 
left ; this shortened thread passes over a thread at r and under one at p, as 
before, and its further course is unaltered in either direction. The same is 
true of the shortened thread made by reuniting the two threads on the right of 
the section. 

The figure is now the projection of a knot of n— 1 crossings having two 
portions, L on the left and R on the right, which are connected by a single 
thread kl, the law of under and over being observed in both L and R 
The course of the thread kl, pursued along its circle small or great through R 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 283 

from k upon R, must bring it back to I upon L through L. But this is clearly 
impossible from want of a second connecting thread ; which proves the proposi- 
tion. 

9. Knots Solid, Subsolid, and Unsolid. — A solid knot is a polyedron, 
art. 7. 

Subsolid knots admit of no linear section but through the two crossings of 
a flap ; through the projections of these a closed curve can be drawn meeting 
the knot in no third point. 

The projections of an unsolid knot admit one or more linear sections either 
through two crossings not on a flap, or through two edges coming from two 
crossings not on the same flap. 

If a projected unsolid V admits a linear section through two edges coming 
from two crossings on the same flap, V is made up of two portions, K and L, 
connected like two links of an ordinary chain, so that K (or L) can be set free 
in its completeness by breaking only one thread of the other. No knot V 
constructed in these pages is such a compound of K and L. Such a compound 
is easily drawn ; in such a V either K or L can be slipped along the thread of 
the other, without twisting a tape, so as to occupy, if the other be unifilar, any 
position upon it. All our unsolicls are composite ; but no severing of a single 
thread will ever set free on one of them a portion which is a complete knot. 

Of solid knots we are not treating. If the apparent dignity of knots so 
maintains itself as to make a treatise on these w-acra desirable, it will be no 
difficult thing to show in a future memoir how to enumerate and construct 
them to any value of n without omission or repetition. The beginner can 
amuse himself with the regular 8-edron, which is trifilar, or with the unifilar of 
eight crossings made by drawing within a square a square askew, and filling up 
with eight triangles. 

10. I consider a knot as given by its projection upon and within any one, 
2-gonal or ???-gonal, of its meshes drawn large, and as having the symmetry of 
that projection. Nor do I trouble myself with inquiring how far that symmetry 
is affected by the law of under and over at the crossings, because, in reading 
the circle or circles of a projected knot, we can take any crossing q as our first, 
and can on beginning to read take either of the threads at q as passing under 
and over the other. A knot in space can be read only as given. 

In my description of the symmetry of our reticulations, I shall assume that 
the reader understands the terms employed. They, with others not wanted 
here, are necessary and sufficient ; they are the only such terms that ever have 
been proposed ; and, for more than twenty years since they were introduced, 
no more suitable terms have offered in their stead. I am quite ready to use 
better ones when they are invented. The symmetry, however, of the figures 
handled in this paper is of itself so evident that the reader will easily satisfy 



284 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

himself, without debate about the terms employed, as to the truth or error of 
my enumerations. 

11. All that we need to add here is on the symmetry of flaps, which are 
2-gons, correctly drawn as two curved lines through the same two points. 

A flap has the symmetry of its undrawn diagonal d through its two cross- 
ings, and may be conceived as standing symmetrically about d, in either of two 
planes at right angles to each other, which contain d. This d may be asym- 
metric, or epizonal, or zonal, or zoned polar, or zoneless polar ; and the flap is 
accordingly asymmetric, or epizonal, &c. The two edges of a flap are unlike 
only when it is asymmetric or epizonal. 

In a zonal flap, a single zonal trace passes through the two crossings ; in an 
epizonal flap, a single zone passes between the crossings. In a zoned polar 
flap, two zonal traces intersect in the centre, the termination of the 2-zoned 
axis. 

In the centre of a zoneless polar flap, an axis of 2-ple repetition termin- 
ates. 

3 A and 4 A have each one zoned polar flap. 

5 A has one epizonal flap. 

G F has one epizonal and one asymmetric flap. 

6 G has two different polar, and one zonal flap. 

6 H has one zonal flap and no other. 

8 S and 8 Q have each one zoneless polar and one asymmetric flap ; so has 8 A/. 

8 AZ; has one asymmetric flap and no more. 

8 Awi has one zoned polar flap and none other — art. 45. 

& Bn has one epizonal, two zonal, and one asymmetric flap. 

8 Bq has one zoned polar and one asymmetric flap. 

8 Bw has three zonal flaps only. 

s Bv and 8 Bw have each one epizonal and two asymmetric flaps. 

8 B?/ has one zoned polar and one zonal flap. 

12. The construction of polyedra and of other reticulations of n summits is 
best apprehended by studying their reduction by fixed rules to antecedents or 
bases of n — i summits. We proceed to the reduction of knots. 

Reduction of an Unsolid Knot Qo/n Crossings. 

In this are two processes, — the clearing away of concurrences, and the 
removal of least marginal subsolids. 

13. Concurrences. — Two or more continuous flaps, each having a crossing 
common to the next, are a concurrence of two or more, except when two or 
three flaps are collateral with the same triangular mesh. Three such flaps on 
a triangle complete the irreducible subsolid 3 A ; and two on a triangle are not 
counted a concurrence. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 285 

When a concurrence of n stands about the (n + k + 2)-gonal mesh F, their 
common collateral, F is reduced by deletion of n — 1 flaps, each conceived to 
vanish by the union of its two summits, to the {k + 3)-gon F', carrying one only 
of those flaps. 

If their collateral F is an (n + l)-gon, it is reduced by the vanishing of n — 2 
of the concurrent flaps to a triangle/ carrying the remaining two. This/ cannot 
lose a flap without losing an edge and disappearing. 

Every concurrence on the unsolid Q of art. 12, whether standing on a 
marginal or non-marginal component of Q, is to be thus reduced, and Q now 
becomes an unsolid Q' without a concurrence, of n — i crossings. 

14. Least Marginal Sections and Least Marginal Subsolids. — Our unsolid Q', 
obtained by deletion of i flaps, has one or more linear sections, marginal or not. 

By a marginal linear section of Q' can be cut away one and only one 
marginal subsolid, on which (art. 9) lies no linear section except through the 
two crossings of a flap. 

By a least marginal section of Q' can be cut away a. least marginal subsolid. 

A marginal subsolid of k crossings all untouched by any possible least 
section, is a least marginal, when no marginal subsolid of fewer than k cross- 
ings untouched by the section can be cut away from Q' by any kind of section. 

15. The Five Kinds of Linear Section of an Unsolid Knot. — These are, 

ffc, which is read, flap on flap close ; 
/, „ „ flap on flap ; 
fe, „ „ flap on edge; 
ef, „ „ edge on flap ; 
ee, ,. „ edge on edge. 

The first letter in these symbols denotes the flap or edge of the least 
marginal subsolid cut away from, or in construction imposed on, the unsolid or 
subsolid charged. 

16. The linear section ffc is the only one that passes through two crossings. 
After making the section ffc, there is a pair of truncated crossings, both on the 
diminished Q' and on the subsolid removed. These are completed into 
tessaraces in the severed portions by replacing each portion on the other by the 
two pairs of edges of two flaps, at the cost of which two flaps the portions were, 
in construction at the section ffc, united to form Q'. 

These pairs are conceived to be so united to the broken threads at the 
truncated crossings as to complete both the severed portions into two knots. 
This can always be done, and needs not trouble us, when we are reducing a 
projected figure of simple lines making tessaraces only. 

If the subsolid S removed at this section ffc has, when completed by its 
restored flap, k crossings, the n — i crossings of the undiminished Q' are made 
fewer by k—2 ; for Q' has lost only the crossings of S not on the section. 



280 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

This S in construction of Q' was counted as a least marginal charge of k—2 
crossings. Two crossings are always lost when in construction a subsolid 
having k crossings is imposed at a section ffc. 

In reduction at this section ffc, this S is a least marginal subsolid of k—2 
crossings along with others of k — 2 removed by any section ff, fe, &c. 

17. Our unreduced Q' of n—i crossings may have in it every kind of least 
marginal section, art. 15. Such section, not ffc, always cuts two edges, making- 
four ends. In every case,ff,fe, ef, or ee, those pairs of ends are conceived to 
be united on either hand into one edge, by which is restored the half-flap or 
the edge cut away in each portion when united by construction, in order that 
every summit should be a tessarace in the completed unsolid. 

The imposition of a least marginal charge by ffc costs four edges of two 
flaps ; by ff, fe, ef or ee it costs only two edges, one on each of the united 
knots. 

No crossing is lost when a charge is imposed by a section ff,fe, ef, or ee. 
All this will be found very clear and easy when we come to constructions, and 
examples will abound. 

18. In. this reduction of Q' all least marginal subsolids, say of k crossings, 
are to be removed without regard to the number of their meshes, which may 
differ while each has added k crossings. And care is to be taken that none is 
cut away which has been loaded with another either on flap or edge, and thus 
made non-marginal. 

When our Q' is thus reduced, it has become Qx an unsolid of n— j crossings 

U>i)- m 

This Q x will in general have one or more concurrences due to the flaps sub- 
stituted for subsolids removed. All these are to be cleared away (art. 13), 
whereby Qx becomes Qi", an unsolid without a concurrence ; and Qi is to be 
treated as we treated Q' in art. 14. 

We shall finally arrive by these reductions either at an unsolid of two 
portions, neither of which is least, which is to be reduced by a final section to 
two subsolids each of c crossings ; or at a ring of flaps which is reducible to the 
fundamental 3 A ; or to a nucleus subsolid or solid knot. We have now to set 
about the reduction of subsolids. 

19. Reduction of a Subsolid of n Crossings by its Leading Flap. — The rule 
is — Remove both edges of a leading flap, or of a leading flap when there are 
co-leaders. By this removal, the two meshes covertical with the deleted flaps 
lose each a crossing ; and if one or both coverticals are triangles, that one or 
both become flaps. The result obtained is a subsolid of n — 2 crossings. 

20. Every flap can be written AB,CD, where A and B (A>B) are col- 
laterals, and C and D (C>D) are coverticals, of the flap. 

We compare first the collaterals of the flaps whose leader is to be found. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 287 

If AxBi, A 2 B 2 , &c, are the pairs of collaterals, the leader has the greatest A, no 
matter what be the coverticals. If several flaps have the greatest A, the leader 
has the greatest B. If several have both A and B greatest, we compare co- 
verticals. If one has the greatest C, it leads ; if more than one, the greatest D 
gives the lead. If no leader can thus be determined, we have to examine the 
collaterals of the A's. The leader has more than any other of the greatest of 
these collaterals ; and so on we go over the collaterals of the B's, the C's, and 
the D's. The leader, if there is only one. is certain to be found. 

I have never had occasion to examine the collaterals of AB,CD. If two 
competitors have these all equal, it is almost a certainty that there is symmetry, 
and no leader, but a set of co-leaders. Where there is no symmetry, no two 
edges or flaps on a knot are alike. 

It suffices, after writing two or more flaps as equally claiming by their AB, 
CD to lead, to place a note of interrogation, and to examine the symmetry, 
which readily betrays itself. The deletion of any one of the co-leaders com- 
pletes the reduction. 

A flap can neither be removed from a knot nor added to it without cutting 
of threads and reunion of ends. But this does not trouble us here, as by art. 2 
we know that every projection making tessaraces only is a true knot, that its 
circles can be read by the rule of under and over, and that the threads of all 
the circles can be drawn in double lines as narrow untwisted tapes visibly 
passing under and over at alternate crossings. 

21. In the converse problem of construction, the question is, in how many 
ways to add, on a knot P' of n — 2 crossings, a leading flap, so as to construct 
without risk of repetition a subsolid of n crossings. The note of interrogation 
written after the comparison of two flaps that can be drawn across two meshes 
of P' is a presumption of symmetry, which is pretty certain to be verified when 
we come to draw in turn our new flaps on P', and to examine the constructed 
P of n crossings as to the leadership of the doubted flap which turns P' into P. 

22. Two things are to be noted here, both in reduction and construction. 
If a flap /on any subsolid is covertical at its crossing a with a triangular mesh 
abc, which carries a flap/ 7 on the edge be, since abc cannot lose a crossing by 
the deletion of/ it thereby becomes itself a flap /" collateral with the flap/'. 
Now a pair of collateral flaps is excluded from all our constructions, because it 
is a circle of two crossings, whose projection represents nothing in space but a 
movable ring through which one thread once passes. Wherefore the flap /is 
indelible or a fixed flap. It cannot be removed, nor be a competitor for the 
lead, either in reduction or construction. 

When two flaps are collateral with the same triangular mesh, both are fixed ; 
for the deletion of either leaves the other hanging by a nugatory crossing which 
admits a forbidden punctual section. The reader can easily verify this. 



288 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

By continuing this reduction of a subsolid by removal of the leading fl ip, we 
must at last arrive either at a solid knot, or at one of the two irreducibles 3 A 
and 4 A, of three and of four crossings. 

23. Construction of Knots o/n Crossings. — The rules for this are the exact 
converse of those above given for reduction. 

First, to construct the subsolids of n crossings, all inferior knots being given 
with their symmetry, we have in the first place to take in turn every subsolid 
P' of » — 2 crossings, and to determine before we draw them the different lead- 
ing flaps that can be added on P'. Knowing its symmetry, we can write down 
and mark on its edges every different pair of points on flap or edge that can be 
joined as the crossings of a new flap, and also the collaterals and coverticals 
which this will have. We make a table of the possible leading flaps, with the 
notes of interrogation that presume symmetry in the P of n crossings to be 
built on P'. Next we draw the leading flaps, thus constructing and registering 
the resulting subsolids P. 

A caution is required here, for the examination of the claim of a new flap, 
ab = 3M, to leadership ; a and b being the crossings of the flap, when one of its 
collaterals is a triangle abc. If c in this triangle is the crossing of a flap cd, cd 
becomes fixed (art. 22), for it is covertical with a triangle^aJ, which carries a 
flap on its edge ab. Care must be taken to exclude this flap cd from claim to 
leadership over ab. 

I was caught in this trap in the art. 41, for I had entered the flap (bd) as 
led by (56), and thus missed the unifilar 8 Gr. Professor Tait found this knot, 
adding one to my first list of 8-fold knots. He first found also the unifilars 
9 A/, gAk, and 9 B^, omitted by a like error in arts. 51 and 56. He also first 
found Dm, which I ought to have constructed along with 9 DZ in art. 61. 

24. In the second place, we take in turn every unsolid P" of n — 2 crossings 
on which a leading flap or flaps can be drawn so as to abolish all concurrences, 
and to block linear section. Such leading flaps will be few. Next we draw 
them all, and thus complete without omission or repetition our list of subsolids 
P of n crossings. This list is the only difficulty of our work ; what follows is 
for every value of n all easy routine, as we shall see ; but it soon becomes too 
tedious by the enormous number of results to be registered and figured. 

25. Next, to construct the unsolids of n crossings which have no concurrence, 
we impose in the first place on the solids and subsolids, and in the second on 
the unsolids, of n — i crossings, each taken in turn as the subject Q' to be 
charged, e charges of least marginal subsolids, all of k crossings, no matter 
what be the number of their meshes, so as to add to Q' ek = i crossings, com- 
pleting an unsolid Q of n crossings without a concurrence. 

The e charges may be all or none alike, or all but one alike, &c. ; and from 
our list of subsolids of k crossings must be selected with or without repetition 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 289 

every possible set of e charges. These, as well as their reflected images when 
required (although such images are neither registered or figured by us), have to 
be imposed in every different posture, by every kind of possible section, ffc, ff, 
&c, on every different set of e flaps or edges that can be selected on the subject 
knot, and in every different order that symmetry permits without repetition of 
results (art. 4), so that when the work is done not one of the unsolids Q of n 
crossings shall have a least marginal subsolid besides the e that we have just 
imposed, nor have a concurrence upon it. 

26. The linear sections by which the charges are imposed may be any of the 
five of art. 15. But, observe, when we use the section^, we are to select the 
charge from our list of subsolids of k + 2 crossings; because {art. 16) two will 
be lost. For other sections our selection of the charges will be from those of 
k crossings. 

27. The number of different postures in which a charge can be imposed on 
Q' depends on the symmetry of the united portions of the Q completed by the 
union. Let e denote the edge or flap of the subject and e' that of the charge in 
all the five sections ffc, ff, fe, ef, ee. The rules are three — 

(1) If one or both of e and e be zoned polar, only one configuration is pos- 
sible by the union ; no second and different (art. 4) can be formed by turning 
the charge C through two right angles about e , nor by using C, the reflected 
image of C, when C is not C. Every knot on which is a zone is its own 
mirrored image. 

(2) If neither e nor e be zoned polar, and if they are not both asymmetric, 
two and two only different configurations can be made by the above variation 
of posture of the charge. 

(3) If both e and e are asymmetric, four different configurations can and 
must be made and registered, due to such variation. 

No more results can be obtained by putting for Q' the reflected image of 
Q' : nothing is so attainable but repetitions or reflected images of knots already 
registered. 

On almost every subject Q' and charge C, though having any symmetry, 
may be found asymmetric, i.e., zoneless and non-polar, flaps and edges, which 
are to be dealt with by the above rules. 

28. The subject Q' to be charged with a set of least marginal subsolids may 
have or not have concurrences. All that is required in order that the com- 
pleted Q shall have no concurrence, is that our number e of charges of k 
crossings shall be large enough to spoil all concurrences on Q', as well as to 
cover at least once every marginal subsolid on Q' which has fewer than k + 1 
crossings. 

In the constructions of this paper, Q and C are one or both symmetric. 
When asymmetries come to be handled both as subject and charge, the number 

VOL. XXXII. PART. II. 3 B 



290 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

of results becomes unmanageably vast long before n the number of crossings is 
out of its teens. 

29. The final operation, after construction of all knots of n crossings with- 
out concurrences, is to take every subsolid and unsolid E, in our lists which has 
n — c crossings and no concurrence, and to add to it in every possible different 
way c flaps making with one or more on R concurrences of every possible 
number of two or more flaps, thereby adding c crossings, and completing the 
number n. This last operation soon becomes impracticable from the number 
of results. 

30. Nothing can be here added that will give so much insight into our 
subject as the actual construction of knots, to which we now proceed, first to 
that of subsolids, and next to that of unsolids of the number n in hand of 
crossings. 

Two Fundamental Subsolid Knots. — The only subsolids that cannot be 
reduced by deletion of a leading flap (art. 19), are those of three and of four 
crossings. These, 3 Aand 4 A( vide Plate XL.), are irreducible and fundamental. 
3 A is a 3-zoned monarchaxine, whose principal poles are triangles not plane, 
which have three common summits and no common edge. 

The unsolid 4 B is formed on 3 A by art. 29, and has a symmetry of like 
description. The secondary 2-zoned poles on either are alternately flaps and 
crossings, being heteroid poles in 3 A and janal in 4 B. 

31. Subsolid and Unsolids of Five Crossings. — The subsolid must be built on 
3 A. The only points that can be here joined by a flap, are either on one flap of 
3 A or on two. We cannot obtain a subsolid by joining the former pair, because 
the constructed knot would be an unsolid having a concurrence of two (art 13). 
We join the latter pair, and it matters not whether we draw our flap in the 
upper or in the lower of the two triangles whose summits are the same three 
crossings, and whose edges are different halves of the three flaps of 8 A. 
Drawing the flap 54, the two flaps of 3 A connected by it become triangles, and 
S A is constructed, a 2-zoned monarchaxine heteroid, whose zoned poles are a 
tessarace and an opposite tetragon. This is the only subsolid of five crossings. 

The unsolid 5 B is by (29) formed on 4 A, and 5 C is made on 3 A. 

32. Knots of Six Crossings. — The subsolids 6 A, &c, must be formed on t A 

and 4 B. This 4 A has a janal 2-zoncd axis through the 
centres of the flaps, and two like 2-ple janal zoneless axes 
through two pairs of opposite mid-edges. It has only one 
mesh, the monozone triangle 342, and the only pair of points 
that can be joined are 5a and 56. 

Drawing 5a, or rather conceiving it drawn, we write 
to determine the leading flap, 

(5a)=43,43; (12)=43,43; (5a)>(12)? 




CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 291 

This is read thus — the flap on 5a has for collaterals 3 and 4, and for coverticals 
3 and 4 ; so has the flap on 12 : which leads ? 
Next, conceiving 56 drawn, we write, 

(56)=43,44; (12) =44,43; (43)=43,44. 

Here by art. 19 (12) appears to be leader, until we observe that it is fixed by- 
art. 22, and cannot be a competitor. 
We therefore write more correctly, 

(56) = 43,44 > (43) =43,44? (12) is fixed; 

which inquires, Does (56), which is 43,44, lead (43), which is also 43,44? 
We consider this second as well as the preceding note of interrogation a pre- 
sumption of symmetry (art. 21). 

Drawing the flap (5a) we obtain 6 A, and the flap (56) gives us 6 B, on both 
of which the leading flap so drawn is marked 56. Observe that in our figured 
subsolids of n crossings, the leading flap is always marked n(n - 1). Our pre- 
sumptions of symmetry are verified in the two results 6 A and 6 B. 

The polar edges of the heteroid zoneless axis of 6 A are evident in the figure. 
The two-zoned axis of 6 B has for faces a flap and an opposite 4-gon. The 
other two flaps of 6 B are like epizonals. 

It was possible to connect by a flap the two edges of the flap 43 in 4 A. But 
this could have completed an unsolid having a linear section through 3 and 4 ; 
and completed it wrong, because no unsolid is ever made by so adding a flap. 

33. We next take the unsolid 4 B, considering whether or no a flap can be 
drawn on it to make it a subsolid of six crossings. Eeadily we perceive that 
by joining two opposite flaps we can both spoil the concurrence and block the 
linear section. This gives us 6 C, which has all the symmetry of the wedge which 
it becomes when an edge is removed from every flap. The three, 6 A C B and 6 C, 
are all the subsolids of six crossings. 

34. We seek now the unsolids of six crossings. To obtain them by least 
marginal charge or charges (art. 25), we have to lay 2 upon 4 and 3 upon 3. 

There is but one charge that can add two crossings only, ^Affc, which means 
4 A imposed (art. 15), by the section Jfc. Imposing this on 4 A we get 6 D, a zoned 
triaxine, whose three janal 2-zoned axes have for poles, one two tessaraces, 
a second two flaps, and the third two 4-gons symmetrical but not plane, which 
have two common summits and no common edge. 

Laying next on 3 A the charge z Aff (art. 15), we obtain 6 E, another zoned 
triaxine, whose janal poles are two edges, two tessaraces, and two hexagons 
alike and non-planar. There is in truth no least marginal subsolid in either 
6 D or 6 E, the two halves of the knot being identical in each. But it is instruc- 



292 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 



tive, and involves no error, here to consider them as cases of the linear sections 
ffcandtf. 

35. We have constructed all the knots of six crossings that are without a 
concurrence, viz., 6 A, C B, 6 C, 6 D, 6 E. Those having concurrences are obtained, 
G F on 6 A, 6 G- and G H on 4 A, and J on 3 A. These nine, 6 A . . . 6 I, along with the 
solid knot 6 J, are the ten jDOssible knots of six crossings. Four of them, as 
Tait has found and drawn them, are unifilar, viz., 6 A, 6 E, 6 F, 6 G; and this is 
read on the figures. The number 12 on each shows that there are 12 steps in 
the circle of the knot, which passes twice through every crossing, once over 
and once under. 6 B, 6 D, and G H are bifilars ; 6 C and 6 J are trifilars. 

36. Knots of Seven Crossings. — The subsolids 7 A, &c, must be built on 5 A, 
&e. The only lines that can be drawn on 5 A here 
given are ff and aa, each 44 ; and af, ae', ee' he, oh, 
each 34. 

By ff, which has no rival, we get 7 A ; whose 2-zoned 
poles are the flap and the tessarace 3333, 

(«a)=44>(12), or (34) = 43; 
(a/)=53,43>(12)=53,43? 
(6A)=43, 43 ><12) =43,43? 

For the; rest, ae' , he, and ee' , 

(43)=53>(«e')=43; 
(43)=44>(5e)=43 and >(ee')=43. 

We 'have to draw, besides ff, the flaps (aa) (af) and (bh), expecting symmetry 
with the two last, which we soon find. 

By (aa) we get 7 B , 

whose 2-zoned poles are this flap and a tessarace. 

By (af) comes 7 C, monozone ; 




By (bh) 



J), 



whose zoneless 2-ple poles are a 4-gon and a 4-ace. Thus there are four sub- 
solids, 7 A, 7 B, 7 C, 7 D, reducible by the leading flap to S A. 

37. On 5 B, annexed, as we cannot allow a concurrence, we can draw only 
(af) and (&/), 

(«/) = 53>(12)=43, and (45) is fixed (art. 22). 
(Z>/)=44,43>(45)=44,43 ? ((12)= 34), 

for (45) is not fixed when (If) is drawn. 

We have to draw (af) and (hf) looking for symmetry 

in the latter. 




CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 293 

(af) gives us 7 E, asymmetric ; 
(hf) „ 7 F, monozone. 

Thus there are six subsolids, 7 A 7 B . . . 7 F, of which we read on their figures 
that 7 C, 7 D, and 7 E are unifilar. 

38. To obtain the unsolids 7 G, &c., without concurrences, we have to lay 2 
upon 5, 3 upon 4, and 2 . 2 upon 3, 

±Affc on 5 A gives 7 G, monozone, 

This is 2 upon 5. We cannot lay the same charge on 5 B destroying the con- 
currence, without completing an unsolid having two marginal charges of which 
we have just imposed only one ; which is forbidden (art. 25). 
For 3 upon 4, 

3 Aff on 4 A gives 7 H : 

z Afe on 4 A gives 7 I; vide the figures. 

Observe that we can impose 3 A only by the sections ff&ndfe; for it has no 
edge to lose at a section ef or ee ; and if we attempt to lay it on a flap h by ffc, 
we merely turn h into a concurrence of two, which is not permitted as a result 
of any charging operation. 

In 7 H and 7 I the 2-zoned and the zoneless 2-ple axes of 4 A, after being 
loaded symmetrically by 3 A, retain their repeating polarity, but from being 
, janal have become heteroid, not janal. 

For 2 . 2 upon 3, we lay on 3 A the two charges iAffc, which stands for 
twice tAffc. The result is 7 J, in which one flap is zoned polar, and two are 
epizonal. Thus there are four unsolids, 7 G, 7 H, 7 I, 7 J, without concurrence. 

39. For unsolids, 7 K, &c, having concurrences, we obtain on 6 A, 7 K ; on 
6 B, 7 L and 7 M ; on 6 C, 7 N ; on 6 D, 7 P ; on 6 E, 7 Q ; on 5 A 7 R and 7 S ; on 4 A, 7 T 
and 7 U ; on 3 A, 7 V ; eleven of them. 

Thus we have 21 knots of seven crossings, of which 6 are subsolids and 15 
are unsolids. Their symmetry and circles are to be read on their figures. 

Twelve of them, 7 C, 7 D, 7 E, 7 G, 7 H, 7 I, 7 L, 7 P, 7 S, 7 T, 7 U, 7 V, are unifilar, of 
which all but 7 I have been found and figured by Tait. See Plate XV., Trans. 
R.S.E., 1876-77, for his eleven figured unifilars, and his reduction of them to 
eight. 

40. The meaning of the symbols ffc, ff, and fe is clear from the figures 
7 G, 7 H, 7 I. In reduction of 7 G, after making the linear section, two flaps have 
to be restored. Also after section of the two parallels in 7 H, the cut portions 
have to be united to make two flaps on the severed knots ; and after section 
in 7 I they have to be united to restore the flap on the charge 3 A and the edge 
on 4 A. 

We shall see an example of the section ef in 9 D^, and of ee in 8 Ak and 9 Di ; 
vide the figures. 



294: REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 




41. Construction of Knots of Eight Crossings. — For the subsolids 8 A, &c, we 
have to draw leading flaps on G A, &c. In 6 A, which is 
figured here, the 2-ple zoneless heteroid axis passes 
through a and e. The only faces are 5641, 634, and 
563, and there is one flap which is asymmetric, hav- 
ing different edges marked / and f. The only different 
lines that can be drawn are 

fa,fh, ca, cb, each 35 ; 
fc and ab, each 44 ; and 
fd,f'c, be, bd, de, dc, each 34. 

The two d's are the same point repeated in the repeated triangles 563 and 124. 

(fa) =53, 53 > (12) =53, 53? 

(fb) = 53>(12)=43; 

(ca) =53, 54>(56)=53, 53 ; (12) is fixed (art. 22) ; 

(cb) =53,44>(56)=53,44? 

(fc) =44, 43 > (12) =44, 43? 
(/'rf) =43, 43 > (12) =43, 43? 

(bd) =43, 54>(12)=43, 53; (56) is fixed (art. 23). 
For the rest, 

(12) leads (ab) ; and (56) leads (fc) (be), (de) and (dc). 
We have to draw seven flaps, expecting symmetry in four cases — 



(ca) gives us 8 E ; 
(bd) „ 8 G; 



(fa) gives us 8 A ; 

(fc) » 8 B; 

W . 8 C; 

(fd) „ 8 D; 

whose symmetry and circles are read on their figures, where the zoneless poles 
on 8 A, 8 B, and 8 D are 55 and 33, 44 and 33, 44 and 44, and the leading flaps 
are marked 78. 

42. We take next 6 B, whose only faces are the 2-zoned polar 1256, and the 
monozone faces 4253 and 124. The only lines drawable 

are, 

fa, ba, lib, each 35, 

ff, aa, bb, ha, each =44, 
and f'b, bb, each =43. 

Here (43) is fixed for every flap that we can draw, 

[The 6 should bo at the base corner.] ^^ ^ ^ ^ each = 44. 

(ba) = 53, 54>(56)=53, 54? (12) and (43) are fixed (arts. 22, 23). 

(hb)= 53>(12)=44and >(56)=43. 

(66) =44, 44>(12) or (56) or (43) ? each=44,44. 

(/)=44,33>(43)=44,33? 

(aa)=44 >(12)=43 and >(56)=43. 




CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 295 

For the rest, 

(56) leads (fa) and (fb) from the flap (12), 

and (12) leads (?>&)= 43. 

We have to draw five flaps, presuming symmetry with (ba), (bb), and (ff). 

(ff) g iv es us 8 H, 

whose three 2-zoned janal axes terminate in the centres of the zoned polar 
flaps and of two pairs of edges 44, 44 ; and 33, 33. 

(Kb) gives us 8 I, asymmetric, 
(bb) gives us 8 J, 

whose two janal zoned poles are 4-gons, the four like janal zoneless 2-ple poles 
being edges 44. We often mean by pole the polar face summit or edge in 

wh'ich an axis ends. 

(act) gives us 8 K, 

having two different zoned polar flaps : 

(ba) gives us 8 L,. 

whose zoneless poles are 44 and 55. 

43. Our next base is 6 C, which has one flap, one triangle, and one 4-gon. 
The only different lines that can be drawn are ff and aa, 
each 44, and /a and aa, each 43. The two/'s are alike. 

(ff) =44, 33 > (23) =43, 33? 

(aa) = 44 >(32) or (56) or (14) ? each =44; 
not (/«)=53 >(14)=5i; 
nor (aa)=43 >(14) = 54. 

We have two flaps only to draw. 

(ff) gives 8 M, 

whose zoned poles are the flaps, the four like zoneless 2-ple poles being 

tessaraces. 

(aa)—A.A gives 8 N, 

whose eight janal secondary 2-zoned poles are alternately flaps and 4-gons. 

44. We have no more subsolids of six crossings. Of the unsolids, we 
find only four, 6 D, 6 E, 6 F, and 6 G, on which a flap can be drawn to block linear 
section. 

We have on 6 D, in \aa, and 14««, 



(aa)=53>(34) and >(56), each =43. 
(aa)=44>(34) or (56) each=43. 

By (aa)=53 we get 8 P. 

By (aa)=44 we get 8 Q, vide the figures. 





296 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 
We have on 6 E, 



By 

by 



(««) = 64>(23) or (45) = 63. 
(fl«) = 55>(12) or (45) = 53. 

(<m)=64 we get 8 Pi, and 
(aa) ~55 we get 8 S. 



Upon 6 F we see that (ab), (ad), (ac), are the only flaps that can block linear 
section and exclude concurrence, 




not 



(«5) = 54,33>(43) = 54,33? 
(ac)=54 >(43)=44, 
(ad) = 63 >(43) = 64. 




Drawing the flaps (ab) and (ac) we get 8 T and 8 U. 
Upon 6 G only (ab) can exclude concurrence. Here (34) is fixed (art. 22). 

(a&)=54>(56)^54? (12) = 34. 

Drawing (ab) we obtain 8 V symmetric as we expected, 
having three different flaps, one zonal, one epizonal, and 
one asymmetric. 

One more subsolid, 8 W, is built on 6 J, which has only 
one edge and one angle. 

We have constructed twenty-two subsolids of eight crossings, 8 A . . . 8 W, 
whose symmetry and circles are seen on their figures. Seven of them are 
unifilar. 

In naming these knots I use an alphabet of 25 letters, omitting the letter 0. 

Thus, 

A, B, . . . z ; Aa, Ab, ... Az; Ba, Bb, . . . ~Bz ; 

are each a set of 25. 

45. For the unsolids 8 X, &c, of eight crossings which have no concurrence, 
we have to lay 2 upon 6, 3 upon 5, 4 and 2 - 2 upon 4. 

For 2 upon 6 we can impose 4 Ajfc on G A once, on G B twice, on 6 C once, on 
6 E once, and on fi F once, but on no other of six crossings, without violating the 
rules in arts. 25, 28. 

i A ff c on e A s ives s x ; 

„ 6 B „ 8 Y and 8 Z ; 
F Ac- 

» 6 » 8 ' 

wliose descriptions are read on their figures. The monozone 8 A& has four 
different flaps, one epizonal upon the marginal charge, and three zonals, in the 
zonal plane. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 



297 



For 3 upon 5, 



3 A/on 5 A gives 8 Ad; 

3 Afe on 5 A gives 8 A/ and 8 Ae ; 

3 Afe on 5 B attempted gives 8 Z 



erroneously, or leaves a concurrence. h Affc on 5 A gives 8 Ag, by arts. 16, 17, 
and 8 A^, art. 27. 

For 4 upon 4, 

Jiff on 4 A gives 8 Ai ; 

4 A/eon 4 A „ 8 A/; 



4 Aee on 4 A 



» 8 



AJc and a AL 



The janal zoned poles on 8 Ai are two flaps, two edges of the 4-gon, and two 

opposite not plane 6-gons. The two poles of 8 A/ are a flap and an edge 33 : 

on 8 Ak the janal zoneless poles are edges 33 : on s Al are two pairs (66) 

and (33) of janal zoneless 2-ple poles ; and a third pair are two 6-gons not 

plane. 

There are two constructions by the charge ^Aee, because neither e nor e 

(art. 27) is zoned polar. 

For 2-2 on 4 (art. 38), 

4 A 2 /c on 4 A gives 8 Am, 

which has all the symmetry of 4 A ; the four 2-ple zoneless janal poles are where 
they were, and the zoned janal poles are the two flaps of the imposed charges. 
Finally, 

J?ffc on 4 B gives 8 An, 

having a janal zoned pole in each flap, and another pair in opposite non-plane 
6-gons. 

8 Ap is the only solid knot of eight crossings, a 4-zoned monarchaxine 
homozone, whose eight identical janal 2-ple zoneless poles bisect eight polar 
edges 33. Thus we have constructed seventeen unsolids without concurrence, 
. 8 X 8 Y . . . 8 An, of which nine are unifilar. 

46. We complete our list of unsolids by art. 29 — 



7 A gives 


! 8 A ?; 


7 B » 


8 Ar, 8 As ; 


7 C , 


s At ; 


7D „ 


8 Au ; 


7 E „ 


8 Av, 8 Aw, 8 Ax 


7E „ 


& Ay, 8 Az ; 


7 (j „ 


8 Ba, 8 B6 ; 


7H „ 


8 Bc, 8 Bd ; 



J 



3 Be, 8 B/ 



7 J gives 


8%. 8 B/i J 


6 A „ 


8 B *> 8 B / ; 


6 B „ 


8 BJc, 8 Bl, g Bm, 8 Bn ; 


6^ » 


8 Bp, gBj ; 


6^ „ 


8 Br, 8 Bs ; 


6 E „ 


8 Bt, 8 Bu ; 


5 A „ 


8 Bv, 8 Bw ; 


4A „ 


8 Bx, 8 By, 8 Bz ; 


5A ,, 


S C(X. 



Of these 36 we have figured only half, the 18 of them which are unifilar ; 

VOL. XXXII. PART II. 3 C 



298 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 



as in the unifilars appears to lie mainly the interest of these knots. The 18 
plurifils (if ever they deserve a name) can easily be drawn by the student with 
the aid of the above list ; and they must be figured by him who constructs the 
10-fold knots, for on many of them flaps can be drawn to make subsolids of ten 



crossings. 



We have found of eight crossings, 

1 solid knot, unifilar, 
22 subsolids, 8 A . . . 8 W, 
17 unsolids without concurrences 
36 unsolids with concurrences ; 

in all 76 8-fold knots, of which 35 are unifilar. 

47. Consfruction of Knots of Nine Crossings. — The subsolids 9 A, &c, are to 

be formed by drawing leading flaps on 7 A, &c. 

The only lines that differ on 7 A here figured are, 

fb and dd, each =44; 

df, dd, db, dg, ge, ee, eb, each =34 : 

2376, 347, 123, and 134 are the only faces. The d's 
are alike, all on the same asymmetric edge 34, which 

has two different sides. 

(fb) = 44, (fd) = 43, and (dd) = 43, have no competitors ; for this (dd) fixes 

(67) (art. 23), 




(dd)=A4, 44>(67)=44, 44 ? 






All the lines =34, except fd and dd, are led by (67). We have four flaps to 
draw, expecting symmetry with (dd) = 44. 

By (cW)=44 we get 9 A ; by (W)=43 we get 9 D ; 

(/&)=44 „ 9 B; „ (fd) , 9 C. 

The symmetry and circles of these four knots are read on their figures. 

48. We consider next 7 B, here drawn. This has the faces 1473, 6745, and 

541, with one zoned polar and one epizonal flap. The 
different lines that can be drawn are, 

ah, aa,fb, bb, and cb, each=53, 
ab,fc, and bb, each =44, 
aa and ae, each =43. 

In bib (bb) =53, 55>(23) or (54) each 53 54 ; (67) is fixed (art. 23) 

(aa) = 53 > (23, 67 or 54) each =44; 

(fc)=U >(23)=43; 
In 6766 (bb) =44, 55>(67)=44, 55 ? (45)=(23)=43. 




CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 299 

For the rest, 

(54) leads (fb), (aa)=U and (a5)=44, 
(67) leads (ab) = 35, (ea) and (cb). 

We have to draw (bb) = oS, (act), (fc) and (£5) = 44, expecting symmetry 
with the last, 



(56) =53 gives 9 E ; 
C/ c ) » 9 F ; 



(66) =44 gives 9 G ; 
(aa) , 9 H ; 




whose symmetry and circles are on their figures. 

49. 7 C annexed has monozone faces 1357, 12467, 354, and asymmetric 
faces 456, 567, and the flap. 

The different lines on it are, 

db, ac, cc, each 36 ; 
aa, ac, be, each 45 ; 
bd, ee, each 44 ; 
ed, eb, each 35 ; 

besides lines 34 that can be drawn in triangles. 

(aa) has no rival : 
in la5, (a5)=63,53>(67) = 63, 53 ? 

in 2ac, (ac) = 63, 43>(67) = 63, 43 ? 

in24ca (ac)= 54>(67) = 53; 

inl2c6 (6c) = 54>(67) = 53 or (12)=43 ; 

(cc) = 63, 44 > (12) or (67) each = 63, 44 ? 

For the rest, (12) or (67) leads them all, as well as all flaps on lines 34. 
We have to draw six flaps, looking for symmetry with three, 

(ab) gives us 9 J ; 

(ac) „ 9 L in 24ca. 
(cc) „ 9 N. 

The symmetry and circles of these are on the figures. 

50. Next comes 7 D here drawn. The polar 4-gon is 5217, and the asym- 
metric faces are 5234, 123, 143. The only different 

lines to be drawn are, 

fd,fh, ch, cd, dg x in ldg, and dg 7 in 7dg, all 53 ; 

fc, dd, dh, gg, all 44 ; 

eg, ei, gi, he, hi, ci, all 43 ; 16 lines. 

(fd) = 53 > (67) =43; 

(fh) =53>(67)=43; 

(cd) = 53, 54 > (32) = 53, 53; (67) = 43; 

(d&) = 53, 54 > (67) = 53, 53, or (32) = 44 ; 

(fa) = 53 > (32) = 43 ; and (67) is axed (art. 23) ; 



(aa) gives us 9 T ; 
In 2ac {ac) „ 9 K ; 
in 216c (6c) „ 9 M ; 




300 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 



in c4h, (ch) = 53,44>(32) = 53, 44 ? (67) is 43 ; 
(/c)=44 >(76) = 43; 
(dh) =U >(76or32) = 43; 
(gg) = 44, 44 > (76 or 32) = 44, 43 
(eg) =43, 53 > (76) = 43, 53? 
(ei) =43, 43 > (76) =43,43? 
(hi) =43, 54>43, 43 ; (23) is fixed (art. 23). 
For the rest, 

(32) leads del, gi, ci, and 7tc=43. 

We have twelve flaps to draw, expecting with three at least symmetry 



(fd) gives 9 P ; 


(fc) 


gives 9 V ; 


(ffl n 9 Q; 


(dh) 


n 9 " J 


(cd) „ 9 R ; 


(oa) 


x- 


^i) » 9 s ; 


(^) 


Y- 

» 9 1 3 


(ch) „ 9 T; 


(ei) 


» 9^; 


(dg 7 ) „ 9 U ; 


(hi) 


„ 9 A«. 




The poles of 9 X are a tessarace and the leading flap. The symmetry and 
circles of all are read on figures. 

51. Our next subsolid base is E 7 appended, on which no two edges are 

alike. Thirty-one different flap-lines can be drawn 
4 on it, namely, 



hd, hf, cd, cc,fe, all 63 ; 

he, be, cf, fd, de, all 54 ; 

ae, ah, Im, Ij, hm, hj, hi, ie, all 53 ; 

ai, hi, eh, jm, all 44 ; 

fm, nf nm, gk, gi, ik,jd,jJc, Jed, all 43 ; 

the lines Im, &c, in the base being supposed dotted. 

(hf) =63, 43 > (67)= 63, 43 ? 54=44 ; 
(cd) =63 >(54)=43; 
(ee) =63 >(54) = 53; 
(be) =54 >(54)=43; 
(k) =54 >(54or67) = 53; 
(cf) =54, 43>(23)=54, 43? (54)=44; 
(/d)=54 >(23 or 54) =44 and >(67)=53; 
(de) =54 > (54) = 53, or (67) = 43 ; (23) is fixed ; 
(Im) = 53, 43 > (67) = 53, 43? (67) =44; 
(dh) = 43, 64 > (54) = 43, 64 ? (67) and (23) are fixed 
(ie) =53, 64 > (54) = 53, 64? 



For the rest, 



(23) leads nf, ah, ae, ai, mh, ef wj, mn ; 
(67) „ hl,he,hi,bd,lj,jd,mf; 
(54) „ gi,gh,ilc,jk,jh. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 



301 



We have eleven flaps to draw, with five queries about symmetry, which 
speedily reveals itself, 



(¥) gives 9 AZ> ; 
(ed) „ 9 Ac ; 
(ce) „ Q Ad ; 
(be) „ 9 Ae ; 

(&e) » 9 4/; 

( c /) » 9%; 



(/rf) gives A7i 

(Im) 
(dk) 
(if) 



» 9 



9 4/ 

,A/fc 

A/. 




The symmetry and circles of all are written on their figures. The poles of 
9 A/ are the tessarace common to the two 5-gons, and the flap which connects 
them : those of 9 A/c are a 6-gon and a 4-ace. 

52. The sixth and last subsolid is 7 F, which has only one asymmetric face 
(1567), and one asymmetric flap (67). The flap (25) is 

epizonal. Eighteen different flap-lines can be drawn : , e_ 

ae, b'd, b'e, of, be, ef, ec, fd, all 53 (bj and be clotted below) ; 

ac, bb, b'f, ee, ed, cj, all 44 ; n 

f, a'/, dd, dj, all 43. 

(6&) = 44>(25) = 43; 

(b'd) in Vd7=53>(2o)=43 and >(34)=44. 

For the rest, 

(25) leads b'e, b'f, cj, ed ; 

(34) leads ae, ee, ec, ac, a'f, dd, and dj in *ldj ; 

(67) leads fd, be in 2>bc,ff,fe, and bj in 4bj. 

We have two flaps to draw, 

(bb) giving 9 Am and (b'd), giving g An, 

whose circles and symmetry are read on the figures. 

53. We betake ourselves next to the unsolids of seven crossings, which, by 
a leading flap, can become subsolids. These are 

r G, 7 H, 7 I, 7 J, 7 K, 7 L, 7 M, 7 N, 7 Q, 7 R, 7 S 

On 7 G annexed can be drawn to block the linear section only three lines, 
which are 

(a&) = 54>(12) = 43; 
in cVl, (cb) = 63, 44 > (54) = 63,43 and > (12) = 43 ; 
in cbll, (c&)=54>(54) = 53 and >(12) = 43. 

We draw three flaps, 

(ab) giving 9 Ap, (cb) giving 9 A.g, and (cb) giving 9 Ar ; 




whose description is seen on their figures. 



302 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

54. On 7 H, here seen, we can draw two flaps only, 

(a&) = 64 (in 566a)>(43) = 63 or (21) = 43. 
(ah) = 55 (in 5625a) > (43) = 53 or (21) = 43. 

One (ab) gives 9 As, the other gives g At. 

Four flaps can be drawn on 7 I annexed, 

(a&) = 64>(56) = 63 or (13) = 53; 
(db) = 55 > (57) = 53 or (13) = 53; 

(ac) = 55 > (24 or 56) =53 and >(13) = 54; 
(«Y) = 64>(57 or 24) = 63 and >(13) = 54. 

Here (ab) gives Q Au ; (ac) gives Q Aw ; 





(db) 



» 9 



Av: 



(do) 



» 9 



Ax. 



Professor Tait does not allow 7 H and 7 I to be different knots, giving a reason 
at p. 158, Trans. R.S.E. 1876-7, which appears to me sufficient wherever it can 
be verified without twisting the tape, or breaking the law of alternate over and 
under. It is true that on the knot in space whose projection is 7 H, the three 
crossings 543 which are found on the thread 67 between 6 and 7, can by 
slipping of the thread be made to appear on the thread 71 ; so that the order of 
the crossings shall be changed from 165435437 . . , the thread passing over at 
15347, to 167543543 . . , the thread passing over at 17534, i.e., making two 
consecutive overs at 7 and 5. The resultant figure in space, although it would 
have 7 I for its projection, would, if I am in the right, be no knot. If I had not 
drawn both 7 H and 7 I, I should have missed some unifilar 9-fold knots, both 
here and in art. 63. 

55. On 7 J, annexed, can be drawn only two lines to make a subsolid, 



(ab) = 54, 44(67) =54,44? (54 = 12) = 43. 

(ac) = 54, 44> (12 or 54) = 43; (67) is fixed. 

(ab) gives 9 Ay, and (ac) gives 9 Az. 



On 7 K, here seen, can be drawn flaps only from /, g, h, or i, so as to spoil 
»s both concurrence and linear section, 



(fa) = 54, 43 > (54) = 54, 33; (12) = 44; 

(fb) = U >(54) = 44; (12) -43; 

(#f() = 54,43>(57)>54,43? (12) = 44; 
(r/c) = 54 > (57) -44, or (12) = 53. 

A flap {/</) can be drawn, but the linear section 74 would remain. For the 





rest, 



(45) leads fc, he, hd ; (75) leads by, ic, id. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 



303 



Here 



(fa) gives 9 Ba ; 

(fb) » 9B&; 



(go) gives 9 Bc ; 
(gc) „ 9 Bd. 

The circles and symmetry are on the figures. 

56. On 7 L, here given, no line can be drawn to spoil the concurrence and 
the linear section but from a or b, 

(ae) = 54 > (23) = 44 and > (67) = 53 ; (54) is fixed (art. 22). 
not (ac)=63 >(23) = 64; 
not (ad) = 54, 33 > (23) = 54, 43; 
not (fy) = 53,53>(67) = 53, 54; 

not (If) = 44 >(67) = 53. 
Here 

(ae) gives us 9 Be. 

On 7 M, here seen, the leading flap must be drawn from a. 



{ad) = 63 > (12) = 44, or (34) = 43 ; 

(a£) = 54 >(12 or 34) = 53 ; (56) is fixed (art. 22). 

(ac) = 54, 43 > (56) = 54, 43 ? (34) = 44. 




Here 




{ad) gives 9 B/, [ab) 9 B^ ; and {ac) 9 B&, the latter symmetrical. 

57. On jN, annexed, 

(ad) = 54 > (42, 26, 17) = 54? 
(26) leads (ab), and (45) leads (ac). 





The only leader 

(ad) gives us 9 Bi, symmetric. 

On 7 P no flap can spoil both concurrence and linear section 
On 7 Q there can be drawn only one leading flap — 

(ab) =56, giving 9 B/. 
On 7 R, here given, 

(«c) = 55>(32 or 17) = 55? 
(ab) is led by (17). 

Here (ac) gives us 9 B/£, symmetric. 
On 7 S, annexed, 

(ac) = 55>(76 or 34) = 54. 
(aJ)=64>(66 or 34) = 64? 

Here (ac) gives 9 B/, and (ab) 9 Bm, the latter symmetric. 
We have constructed by their leading flaps sixty-three subsolids of nine 
crossings, of which thirty are unifilars, bearing on their figures the number 18. 




304 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

58. We demand next the number of the imsolid 9-fold knots, and first, 
of those which have no concurrence. 

To construct these we are to lay 2 upon 7, 3 upon 6, 4 and 2 2 upon 5, and 
32 upon 3. 

For 2 upon 7 (art. 34) imposing 4 Ajfc, we get 



On 7 A , 9 B» ; 

„ 7 B , 9 Bp and 9 B£ ; 

„ 7 C , 9 Br; 

„ 7 1) , 9 os ; 

„ 7 E , 9 B£ , 9 B% , 9 Bv : 

„ 7 F , 9 Bw , 9 Baj ; 

„ 7 tx , 9 by ; 

j) 7 tl > gt)2! , g^<^ j 



On 7 I , 9 C5 , 9 Cc ; 
„ 7 K. , 9 La , 9 Le ; 
„ 7 L , 9 C/ ; 
„ r M, 9 C^; 
„ 7 JN , gL/i/ ; 

„ 7 R , qLj . 



On 7 J we do nothing, because we cannot cover both its least marginal 
charges ; and nothing on 7 P, because we cannot both spoil the concurrence and 
cover the least marginal charge. 

59. For 3 upon 6, the charge must be 5 Affc (art. 26) or 3 Af, or 3 A/e, 



5 Affc on 6 A gives 9 C& and d Cl ; 

C B „ 9 Cm , d Cn , 9 Cp ; 



» 0^ » 9^2 • 

On 6 D we cannot cover both marginals 4 A/c . 
On 6 E we cannot cover both. 

On 6 F, 5 Afc imposed to spoil the concurrence would be 5 A1fc on 3 A 
wrongly constructed by one charge 6 Affc only. 

On 6 G we cannot both spoil the concurrence and cover the least marginal. 
On 6 H it requires two charges to spoil the two concurrences. 
Next, for 3 upon 6 again, 

3 A/ on C A gives 9 Cr; 

3 A/e on 6 A „ 9 Cs , 9 Ct , 9 Cw , 9 Cv , 9 Cw ; 

for the e charged on A (art. 41) is in turn every different edge, a,£,c,6?,0. 



s Aff on 6 B gives 9 Ca; , 9 Ct/ ; 
s Afe on C B „• 9 Cz , 9 Da ; 



3 A/on 6 C 



,D6: 



3 A/e on C „ S)c : 



3 A/on c F „ 9 T>d; 
3 Afe on fl J „ 9 De . 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 



305 



60. We have next to lay 4 and 2 -2 upon 5, 

4 A/on 5 A gives 9 D/; 



A e f 0n 5 A . 


. £>9\ 


4 A/e on 5 A , 


, Q Dh; 


4 Aee on 5 A „ 9 Di . 



4 A 2 j/e on 5 A gives 9 D/ (art. 38). 
4 A 2 / C on 5 B „ ,m. 

5 B was made (art. 31) by adding a concurrence to 4 A ; but it is also 4 A/fc 
on 3 A, though improperly made (art. 38) ; and as we have two charges to im- 
pose, we can both spoil the concurrence and cover the least marginal of 5 B, 
thus making 9 D&. 

61. Finally, we have to lay 2'3 and 3*2 upon 3, 

5 A?ffc on 3 A gives 9 DZ and 9 Dm. 

z A?ff on 3 A gives 9 Dw. These lay 2 - 3 on 3. 

4 A 3 /c on 3 A gives Dp. This lays 3-2 on 3. 

In 9 D/, 9 Dm, and 9 T>n the symmetry is maintained about one of the 2-zoned 
axes of 3 A, though not a 2-zoned symmetry. 

We have constructed 115 9-fold knots without concurrences, of which 63 
are subsolids, and 52 are unsolids without concurrences. Among the 63 are 
30 unifilars, and among the 52 are 25, making 55 unifilars without concurrences. 

62. There remain only the 9-fold unsolids which have concurrences. 
The number of ways in which a knot K' of n-c crossings can be made by add- 
ing c concurrences of flaps into K of n crossings is easily seen when the 
symmetry of K' is given, K' having no concurrence — 

8 V gives 9 Fc , 9 Fd , 9 Fe ; 



8 A gives 9 D<7 






8 B „ 


9 Dr; 






8 c „ 


9 Ds , 


9 T>t; 




8 D » 


9 ~Du; 






8 E „ 


9 T)v , 


9 Dw 


j 9-Lte j 


8 F „ 


9%- 


9 T>z; 




8^" » 


9 Ea , 


9 EZ>, 


9 Ec; 


8 H „ 


gEd; 






8 I - 


9 Ee, 


*W, 


9%; 


8 J „ 


9 E7i; 






8 K „ 


9 E* , 


9 Ey, 


■Bfc; 


8-L » 


9 E£ , 


9 Era 


> 


8 M „ 


9 E% 






8 N „ 


9 E i> 






8 P ,, 


9 E ? 


» 9 Er ; 




8 Q >, 


9 Es, 


9 E£; 




S R 


9 E« 


, 9 E« 




8 s „ 


9 Eiw 


> Q^ X 


j 


8 T „ 


9%. 






8 U „ 


9 Es , 


9 Fa, 


9 F&; 



8 w 
8 x 

8 Y 

8 z 

8 Aa 

8 A& 

8 Ac 

8 Ad 

8 Ae 

8 A/ 

s A # 
s Ah 

8 Ai 

8 Ay 

6 Al 

8 A??i 
Q An 



•f/; 

9 % , fl Ffc ; 

9 Fi, 9 F/, 9 Fft; 
9 FZ , 9 Fm ; 
9 ¥n , 9 Fp ; 
9 F ? , 9 Fr , 9 Fs ; 
9 Yt , 9 F% , 9 Fv ; 
9 Fw , 9 F« ; 
9*V , 9F2 ; 
9 Ga , 9 G& , 9 Gc ; 
qGcI ', 
9 Ge; 

9 G /5 

fig , 9 G/t ; 
9 Gi; 

9G/; 
9 G# ; 
9 G£ , 9 Gm . 



VOL. XXXII. PART II. 



3D 



306 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

63. We have next to add two concurrences of flaps to all of 7 A, &c, on 
which is no concurrence — 

7 A gives Q Gn ;, 

7 B „ Gp , 9 Gg , 9 Gr , 9 Gs ; 

rj\j „ $*-*£ > ^yxU 5 

7 D „ 9 Gv , Q Gw ; 

7 E „ 9 Gx , 9 Gy , 9 Gz , 9 Ha , 9 H& , 9 Hc ; 

7 F „ 9 Hd , 9 He , 9 H/ , 9 H<7 ; 

7 G „ 9 Hh , 9 Hi , 9 H/ ; 

7 H „ 9 Wc , 9 H7 , 9 Hm ; 

7 I „ 9 H» , 9 Hj? , 9 Uq , 9 H> ; 

7 J „ 9 Hs , B.t , 9 Hm , 9 Hv . 

The number of results in any of the above cases of this article is that of the 
different flaps which can be made a concurrence of three plus the number of 
different pairs of flaps that can be made each a concurrence of two. 

64. We have next to place three concurrences of flaps on 6 A, &c, four on 
5 A, five on 4 A, and six on 3 A — 



C A gives 9 Hw , qH.x ; 






6 B „ 9 H?/ , 9 H2 , Q la 


9 16 , qIc 


ld; 


0^ » 9* e > oV ' 9^9 > 






G D „ 9 I7i , 9 K ; 






6^ ,, a!/ s sJ& • 







5 A gives 9 I/ , 9 Im , Q ln ; 
4 A » $P > 'M > o Ir ; 
3 " 9 ■ 

Finally, there is one solid knot, J.t. 

The number of 9-fold knots that have concurrences is 128, of which we 
have figured only the 70 of them which are unifilars. The rest will have to be 
drawn if the census of unifilars is carried to higher values. This can easily be 
done. 

We have found 244 knots of nine crossings, viz. : — 

1 solid knot, 
63 subsolids, 

52 unsolids without concurrences, 
128 unsolids with concurrences. 



Of these 244— 



30 + 25 + 70 + 1 = 126 are unifilar. 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 



307 



I think that no difficulty will present itself in the construction of higher 
w-folcl knots, which has not been met in the preceding pages. 

Here follow the abbreviations used in the descriptions of symmetry : — 



Moncli. for Monarchaxine. 
Triax. or Tri. for Triaxine. 
Triarch. for Triarchaxine. 
Zo. for Zoned. 
Az. for Azonal, or Zoneless. 



Mox. for Monaxine. 

Mo?,, for Monozone. 

Horn, for Homozone. 

Hct. for Heteroid, not janal. 

2p. for 2-ple, repetition about an axis. 



POSTSCRIPT, September 1, 1884. 

65. As it is a brief matter, it may be worth the while to show how all solid 
knots can be constructed without omission or repetition. 

Solid Knots, Prime and Non-prime. — A solid knot Q of n crossings is prime 
or non-prime according as it has or has not a crossing or summit A3B3, A and 
B being any meshes. 

Lowest Triangle of a Solid Knot Q. — It is easily proved that no solid knot 
has fewer than eight triangles. The triangle L of Q is ABC , DEF , where 
ABC are the three covertical faces and DEF the collaterals of L, the lesser 
being written before the greater in both triplets. 

If L' be another triangle of Q, the lower of LL' has the least A, whatever 
be the other five faces. If A = A', the lower has the least B. If also B = B', 
the lower has the least C. If ABC and A'B'C are alike, the lower has the 
least D, and so on. 

If the six faces are alike in both, it is wisest, and almost sure to be right in 
construction, to presume that L and L' are identical, or one the reflected image 
of the other, by the symmetry of Q, which is soon decided. If they are not thus 
proved alike, an examination of the collaterals of ABCDEF cannot fail to 
determine the lower triangle. The one whose A, or, if required, whose B, &c, 
has the lowest collaterals is the lower. 

66. Reduction of a Solid Knot Q. — The simple rule is, efface the edges of 
the lowest triangle L of Q, or of a lowest when Q has a symmetry. 

Such reduction of a prime solid knot Q of n crossings gives us a subsolid or 
an unsolid knot P of n-3 crossings, which has one, two, or three flaps, 
according as the effaced L had one, two, or three covertical triangles : and L 
must have one, or, by our first definition (65), it cannot be lowest on Q. 

Such reduction of a non-prime Q gives either a non-prime P' or a prime 
solid knot P of n-2 crossings ; but I am not certain that this can ever be P'. 



308 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND 

67. Construction of Solid Knots Q of n Crossings. — The rule is the converse 
of the preceding. Add to the subject P of w-3 crossings, whether P be solid, 
subsolid, or unsolid, a lowest triangle of the result Q, occupying three mid- 
edges of a mesh of P. I am* not certain that when P is non-prime such addi- 
tion can ever be made. 

In order that Q may be solid, P must have fewer than four flaps, which, if 
more than one, must be collaterals of one mesh. If P has only one flap, it is 
collateral with two meshes, alike or different. Such a P must not be unsolid. 

It may be that several different lowest triangles of Q may be drawn upon P, 
giving as many different Q, or that no lowest of Q can be drawn on P. In this 
case P is no base, and in construction is useless. No knot Q is reducible to it 
by deletion of a lowest triangle of Q. Examples are given below. 

68. We proceed to construct on our figured knots P every possible solid 
knot Q. 

Our only knots which have fewer than four flaps, all of which stand about 
one mesh, are 3 A ; 5 A ; 6 F, 6 J ; 7 A, 7 C ; 8 R, 8 T, 8 W, s Ad, 8 Ag, 8 Ap, 8 Aq, 8 At ; 
9 A, 9 B, 9 C, 9 I, 9 J, 9 K, 9 L, 9 N, gBm, 9 Bn, 9 D<?, 9 D/, 9 E?/, 9 F/, 9 Gd, Q It ; thirty of 
them, of which 8 Aq, 9 E?/, 9 F/are not figured, but can easily be drawn (arts. 46, 
62) on 7 A, 8 T, and 8 W— 

3 A gives the solid 6 J ; 

5 A „ 8 Ap ; 

G F „ Q lt ; see the three figures ; 

7 A „ 10 A , zo. tri. 4 4 3 G , (446) ; 

7 C „ 10 B , 5 zo. monch. horn. 5 2 3 10 , (20) ; 

and also 10 C , az. tri. 4 4 3 8 , (6 , 14) ; 
8 R gives the solid n A , 2 zo. mox. het. 4 5 3 8 , (6 , 6 , 10) ; 
s Ad „ U B , 2 zo. mox. het. 5 2 43 10 ,(4,4,14); 

8 At „ n C , moz. 54 3 3 9 , (22) ; 

n A „ 12 A , moz. 54 4 3 9 , (4 , 20) ; 

9 B „ 12 B , az. tri. m s , (24) ; 

9 J „ 12 C,asym. 5 2 4 2 3 w , (24) ; 

12 D, 6 zo. horn. 6 2 3 12 , (888) ; 
B K „ 12 E, moz. 54*3°, (10, 14) ; 

9 L „ 12 F, 2p. mox. het. 4 6 3 8 , (G, 18) ; 

n N „ 12 G, 3 zo. monch. 4 6 3 8 , (6666) ; 

Bm „ 12 H , zo. triarch. 4 6 3 8 ,(6,6,6,6); 

9 De „ 12 I , 2p. mox. het. 5 2 4 2 3*° , (4 , 4 , 16) ; 

9 Et/ „ 12 J , 2 zo. mox. het. 5 2 4 2 3 10 , (10 , 14) ; 

9 F/ „ 12 K , 2p. mox. moz. 4 6 3 8 , (24) . 

We have thus twenty prime solid knots, of fewer than thirteen crossings, 



CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 309 

made on eighteen of our thirty inferior knots. The remaining twelve, viz. — 

6 J , 8 T , g W , s Ag , 8 Ap , s Ag , C 9 , 9 I , 9 Bw , 9 ~Dl , 9 &d , 9 lt , 

are found to be no bases. 

In 10 A above, 4 4 means 4444, and the circles are in parentheses. 

No non-prime solid knot has fewer than sixteen crossings. The simplest is 
4 10 3 8 , 4 zo. monch., in which two opposite 4-gons are each covertical with four 
triangles, the triangles being four pairs of collaterals. 

In order that a prime solid knot P may be a base, it must have not more 
than three summits A3B3, which must be so placed that, by drawing a lowest 
triangle of the non-prime Q to be formed, every pair of covertical triangles 
shall disappear. 

All non-primes can be easily constructed by our simple rule without 
omission or repetition when the primes of more than twelve crossings are 
before us. 

This may suffice on solid knots until their value in electricity and magnetism 
is so enhanced as to call for a formal treatise on the whole subject. 



VOL. XXXII. PART II. 3 E 



. Soc . Edm T 



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Soc.EdinT 



Vol. XXXII, PI XLI1I. 




T.HuOiLiW Zim r 



( 311 ) 



XVIII. — On the Approximation to the Roots of Cubic Equations by help of 
Recurring Chain- Fractions. By Edward Sang. 

(Read 7th January 1884. ) 

In the twenty-ninth volume of the Society's Transactions, at page 59, Lord 
Brouncker's process for finding the ratio of two quantities (commonly known 
as the method of continued fractions) is extended to the comparison of three or 
more magnitudes. It is there shown that recurrence, which was believed to 
belong exclusively to equations of the second degree, extends to those of higher 
orders, and examples of this extension are given in determining the proportions 
of the heptagon and enneagon. 

In the present paper it is proposed to show the application of this extended 
method to equations of the third degree. 

If there be a progression of numbers A,B,C,D,E,.... formed by 
means of the multipliers p , q , r , according to the scheme : — 

rB+qC+pT)=E 
rC+qD+pE=F, 

and if the number p be greater than either q or r, the terms will approach to 
be in continued proportion, and their ultimate ratio will be the positive root of 
the equation 

x z — px 2 — qx — r = , ..... (1) 

independently of the values assumed for the initial A , B , C . The actual pro- 
gression may be regarded as the sum of three series having the initials A, 0, 0; 
, B , ; and , , C respectively. On developing the term, we find that the 
coefficient of A in the n\h term is r times that of C in the preceding or n—lst 
term ; while the coefficient of B is compounded of q times the n — 1st, and r 
times the n — 2d coefficients of C. Hence we need only to compute the series 
beginning with , , 1 , in order to have the means of compounding any term 
of a progression formed with the same multipliers. 

VOL. XXXII. PART II. 3 F 



312 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 

The successive terms of the elementary progression are easily found to be 
[0]-l 

W-p 

[2] = P 2 +2 

[3] = p 3 + 2pq +r 

[4] = p 4 + 3p 2 q +2pr + q 2 

[5] = p 5 + Ap 5 q + 3p 2 r + 3pq 2 + 2qr 

[6] = p 6 + 5p i q +4p 3 r + 6p 2 q 2 +6pqr +q 3 -\-r 2 

[7]=p 7 +6p 5 2 +5p i r + 10p 3 q 2 + 12p 2 qr +4:pq 3 + 3pr 2 + 3q 2 r 

[8] = p 8 +7p 6 q +6p 5 r +15pY +20p 3 qr +10p 2 q s +6p 2 r 2 +12pq 2 r +q i +3qr 2 

and the general form of the nth term of the progression having the initials 
A , B , C , is, C being regarded as the zero term, 

[n-l]rA+{[n-l]q + [n-2]r}B + [n]C 
or 

[n-2]rB + [n-l]{rA+qB} + [n]C . 

But the elementary progression alone suffices to determine the value of the 
ultimate ratio 1 : x . 

This process is applicable directly only to equations having suitable coeffi- 
cients. In the case of pure equations, those whose qusesitum is the cube root 
of some number, the coefficients p and q are both zeroes, and the progression 
becomes 

, , 1 , , , r , , , r 2 , , , r 3 , &c, 

which contains the truism that the ratio 1 : r ; r:r*; is triplicate of that of 
which we are in search. 

In order so to change the form of an equation as to fit it for the application 
of this method, we modify Lagrange's process in a manner which may be best 
explained by examples. 



Let it be proposed to extract the cube root of the number 2. 
In the equation 

x 3_0a;2_0a;-2 = 0, 



a . 



we may write -y in place of x, so as to give to it the form 

a z -0a 2 b-Qab 2 -2b 3 = O, 

in which, if b represent the side of a cube, a stands for the side of the double 
cube. 



CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 313 

Here, in order to find the ratio of a to h, we, following Brouncker's plan, 
try how often b is contained in a. Clearly it is only once, with something 
over. We therefore write a = lb + c, and get, by substitution, 

l&3_ 3& 2 f _ 36c 2_ c 8_ 0; 

an equation easily managed. The ratio of c to b is now obtained from a 
progression regulated by the multipliers r=l , q = S , p = 3 ; thus 

0, 0, 1, 3, 12, 46, 177, 681, 2 620, 10 080, &c; 

so that if any one term — say 177 — be assumed for c, the succeeding term, 681, 
is approximately the corresponding value of b; but a = lb + c, wherefore 858 is 
the corresponding value of a. In this way we form the series — 



(0) 


(1) (2) 


(3) 


(4) (5) 


(6) (7) 


(8) (9) 


1 


1 4 


15 


58 223 


858 3 301 


12 700 44 861 


' 0' 


1' 3' 


12' 


46' 177' 


681' 2 620' 


10 080' 38 781 


(10) 


(ID 


(12) 


(13) 


(14) 


(15) 


187 984 


723 235 


2 782 518 


10 705 243 


41 186 518 


158 457 801 & 



149 203' 571032' 2 208 486' 8 496 757' 32 689 761' 125 768 040 

approaching very rapidly to the cube root of 2. 

Among these we notice that each member of the terms (3) , (6) , (9) , (12) , 
(15) is divisible by 3. On simplification, these terms, with the prefixes 

i_ , ^ , form a series progressing according to the scheme r = 1 , q — — 3 

p = 57 ; thus 

(3) (4) (5) 

16 287 927 506 52 819 267 
12 927' 736 162' 41922 680' 

converging still more rapidly to the required root. The term (2) is true to 
within the accuracy of five-place logarithms, the defect being -000 0032. The 
next term (3) passes beyond the exactitude of seven-place tables, its loga- 
rithm being in excess by '00000 00157 . The excess in the case of (4) is 
•00000 00000 31409 , which could not be detected with the ten-place tables ; 
while (5) gives a defect of "00000 00000 00053 , as tested by my manuscript 
tables to fifteen places. The errors are two in defect, two in excess, and so on. 





(0) 


(1) 


(2) 


+1 





5 


286 


-i' 


0' 


4' 


227' 



The roots of numbers immediately above or below a cube are very readily 
found. Thus for the cube root of 9 the equation becomes a? — 9b 3 = 0; whence 
a = 2b + c, and 

b s -12h 2 c-6bc 2 + lc 3 =0. 



314 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 

Hence for a progression converging to the ratio b : c we have the multi- 
pliers r=lj ^ = 6, p = 12, giving the series 

, , 1 , 12 , 150 , 1 873 , 23 388 , &c. ; 

and hence, converging to the ratio of a : b , we have the progression 

(0) (1) (2) (3) (4) (5) (6) (7) (8) 
1 2 25 312 3 896 48 649 607 476 7 855 502 94 719 529 
0' 0' 1' 12' 150' 1873' 23 388' 292 044' 3 646 729' 45 536 400' 



(9) (10) (11) (12) 

1182 754 836 14 768 960 708 184 418 777 041 2 302 821 843 576 
568 609 218' 7100175 745' 88 659 300 648' 1107 081271464 



, &c. 



Here the terms (3) , (6) , (9) , (12) are reducible by the common divisor 6, 
and form the progression 

(0) (1) (2) (3) (4) 

_2 52 101 246 197125 806 383 803 640 596 
-1' 0' 25' 48674' 94 768 203' 184 513 545 244' 

which proceeds according to the multipliers r = l , q— — 3 , p — 1947 . 

This convergence is so rapid that the error of the term (2) cannot be 
detected by help of the ten-place logarithms ; that of (3) is beyond the 
precision of the fifteen-place tables. 



In the case of the number 7 , which is less by unit than the cube of 2 , the 
convergence is somewhat slower. For the equation 

a 3 -7P=0 

it is convenient to take the first measure in excess, and to write a = 2b— c, 
which gives 

b 9 -12b 2 c + 6bc 2 -c 3 =0; 

so that the progression, by help of the multipliers r — \, q=—Q, p — \% 
becomes 

(0) (1) (2) (3) (4) (5) (6) (7) 
-1 2 23 264 3 032 34 823 399 948 4 593 470 
' 0' 1' 12' 138' 1585' L8 204' 209 076' 2 401273' 

(8) (9) (10) (11) (12) 

52 756 775 605 920 428 6 959 097 956 79 926 409 679 917 968 248 840 &c 
27 579 024' 316 749 726' 3 637 923 841' 41782 166 760' 479 875 207 800' 



CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 315 

of which the terms (3), (6), (9), (12) give, on being simplified, the pro- 
gression 

(0) (1) (2) (3) (4) 

-2 44 66 658 100 986 738 152 994 708 140 
1 ' 0' 23' 34 846' 52 791621' 79 979 201300' 

for which the multipliers are r=l , q— - 3 , and jp — 1515 . 



In order to get a clear view of the general principles here involved, we 
shall propose to extract the cube root of n 3 + 1 . 

The equation a 3 — (n s + l)b 3 = Q , gives, for the first approximation, a = nb + c, 
whence 

b 3 -3n 2 Wc-3nbc 2 -c 3 = 0, 

so that the multipliers are r = l , q = Sn, p = 3n 2 , which give, converging to the 
ratio of b : c, the progression 

0, 0, 1, Ziv 1 , 9?i 4 +3tt, 27» 6 + 18w 3 + l, &c, 

and consequently, converging to y/(n s + l), the series of fractions 

(0) (1) (2) '(3) (4) 

_1_ 0_ n_ Sn 3 + 1 9n 5 + 6n 2 27w 7 + 27^* + 4n, 

' ' 1 ' 'in 2 ' 9n* + 3n ' 27» 6 + 18ti 3 + 1 ' 

(5) (6) 

81w 9 + 108ffl 6 + 33ffl 2 + l 2437^ 1 +40ow 8 +189to 5 +21w 2 
81n s + 81n 5 + 15n 2 ' 243m 10 + 324% 7 -j-108^ + 6» ' 

(V) 
729^+1 458rc 10 + 918^ 7 +189« 4 +7rc 
729% 12 +1215?i 9 -|-594?i 6 +81#+1 ' 

(8) 
2 187?i 15 +5 103ft l2 +4 050^+1 242^ g +H7ft 3 +l 
2 187» M +4 374w n + 2 835% 8 +648» 5 + 36% 2 ' 

(9) 
6 561-» 17 +17 496rc 14 +16 767ro"+6 885?t 8 +l 107rc 5 +45w 2 
6 561n 6 + 15 309«, 13 +12 393w 10 +4 050» 7 +459w 4 +9?i ' 

Here we observe that the numerators of the terms (3), (6), (9) are divisible 



316 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 

by 3n\ the denominators by 3n, and hence, for the value of — — ■ — there 
comes out the progression 

+ 1 _0_ 3n 3 +2 81n 9 + 135?^ + 63^+7 
-1' 0' 3?i 3 +l' 8l?i 9 +108?i 6 + 36?i 3 + 2' 

2 187^ 15 + 5 832w l2 + 5 589?i 9 +2 295?t 6 + 369^ + 15 
2 187w 15 +5 103« i2 +4 131» 9 +1350?i 8 + 153ti + 3 ' 

the multipliers for which are 

r = l, q=-3, p = 27n 6 + 27n 3 + 3, 
V(n 3 — 1) 

and similarly we find for ±L ^~ , the multipliers to be 

r=l, q=-3, p=272 6 -27n 3 + 3, 
with the initial terms 

-1 _0_ 3n 3 -2 
+ 1 ' 3n 3 -l : 

these results agreeing with what has been found in the cases of 9 and of 7. 

It may also be observed that each third term of these second series is 
reducible by 3, and that they form a progression converging still more rapidly. 

When the proposed number differs from a complete cube by more than 
unit the extraction of the root is more complicated. As an example, we shall 
take the number 3. 

In the equation « 3 — 3£ 3 = 0, on putting a—lb + c we get 



or 



-2b 3 +3b 2 c + 3bc' i + lc 3 = 0, 



fi2_!_&2 c _!_j c 2_-|. c 3 == (), 



whence the multipliers 

or, more conveniently 
from which the progression 



r- 2"-. 9= T , PS 



r=-8>9 = l[>P=-2> 



— ^ ®l 303_ 1 371 6 199 28 035 

' ' ' 2 ' 4 ' 8 ' 16 ' 32 ' 64 ' 128 ' ' 



CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-ERACTIONS. 317 

the numerators being got from the multipliers 4, 6, 3, while the denominators are 
powers of 2. From this, since a = b + c, we have the approximations to JS 

(0) (1) (2) (3) (4) (5) (6) (7) (8) (9) 

1 j5 21 97 437 1977 8 941 40 433 182 853 
"0 ' 1 ' 3 ' 15 ' 67 ' 303 ' 1 371 ' 6 199 ' 28 035 ' 126 783 ' 



(10) (11) (12) 

826 921 3 739 613 16 911777 
573 355 2 592 903 ' 11 725 971 



, &c. 



Here, as in the preceding cases, each third term may be simplified,. the pro- 
gression being 

7_ 659 60 951 5 637 259 
1 ' 5 ' 457 ' 42 261 ' 3 908 657 ' ' 

for which the multipliers are r = 64, q— — 48, /> = 98. 

Here the approximation is comparatively slow, the less accurate terms being 
largely combined with the more accurate ones. 

To carry Brouncker's process one step farther, let us try how often b con- 
tains c; for b = lc , the above equation gives + 5c 3 instead of zero; for b = 2c, 
the result is + 3c 3 ; but for b = oc, we get - 17c 3 , wherefore b contains c twice 
with something over ; we therefore write b = 2c + d. The substitution gives 

+ 3c 3 - 9c 2 d - 9cd 2 -2d s = 0, 
or 

c s -3c 2 d-3cd 2 -^d s = Q. 

The multipliers hence resulting are 

2 
r = -g, 2 = 3, p = 3, 

giving the progression for d : c 

, , 1 , 3 , 12 , 45-| , 175 , 670 , 2 565-i , &c, 

but a — dc + d, b = 2c + d, wherefore the ratio of a : b is given by the pro- 
gression 



318 



EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 



(0) (1) (2) (3) (4) 



(5) 



(6) 



(7) 



0^ 
' 



o 

2 ' 



10 

7 ' 



39 

27' 



149 



570| 2 185 



8366J 
1515' 5 8001' 



(8) (9) (10) (11) 
32 034$ 122 659 469 657| 1 798 306f f 



(12) 
6 885 667f 



22 211* ' 85 047 ' 325 622if 1 246 806^1 ' 4 774 255 



, &c, 



converging much more rapidly. 

Lagrange's application of Brouncker's method may be still farther con- 
tinued, as in the following scheme : — 



0= a 3 - 0a 2 b- Oab 2 - 3 ¥ 

0=- 2b 3 + 3b 2 c + 3bc 2 + lc 3 
0=+ 3c 3 - 9c 2 d- 9cd 2 - 2d 3 
0=-29d 3 + 18d 2 e + 18de 2 + 3e 3 
0= + 10e 3 -33c 2 /-69c/ 2 -29/ 3 



a = lb +c 
b = 2c+d 
c = 3d + e 
d~U+f 
e=4:f+g 
&c. 



until we arrive at some equation promising greater facility or greater rapidity. 
The last of the above gives 

r = 2.9 ; ? = 6.9 ; p = 3.3 ; 

with the condition a = 13e + 10/; b = 9e + 7/ 



For the cube root of the next number, 4, we have 



a 3 - 0a 2 b- 0a& 2 -46 3 =0, 

- 3b 3 + 3b 2 c + 3bc 2 + lc 3 =0 
+ 4 c 3 - 0c 2 d- 6cd 2 - m 3d 3 =0 

- 5d 3 + 6d 2 e+ 12de 2 + 4e 3 =0 
+ 12 e 3 - 24e 2 /- 24c/ 2 - 5f 3 = 

- 53/ 3 + 24/ 2 ^/+ 48/^ + 12^ = 
+ 31g 3 - 63g 2 h-135gh 2 -53h 3 =0 
-188h 3 + 324h 2 i + 2Wd 2 +31i 3 = 

&c. 

The equation in e and /put in the form 



Cl = lb + C 

b = lc +d 
c = ld + e 
d = 2e+f 
e=2f+g 

g=3h + i 

h=2i + Jc 

&c. 



e 2 -2e 2 f-2c/ 2 -^f 3 =0, 

5 
gives the multiplications p=q7 » <7 = 2 , P = 2 > an d these, along with the con- 
ditions 

a = 3e+3/; Z> = 5e+2/; 



CUBIC EQUATION'S BY HELP OF RECURRING CHAIN-FRACTIONS, 
produce the progression 



319 



5 ' 12' 



54 
34 ' 



94ft 



414ft 1 150^ &c 
261ft ' 724f ' 



converging rapidly to the value of 1/4. 



For the cube root of 5 the equations are 

a 3 - 0a%- Oab 2 - 5& 3 = 
_ 4&3 + 3 £2 C+ 3hc 2 + lc s = 

+ 3c 3 - 3c 2 d- 9cd 2 - 4^ 3 = 
— 10^ 3 + 15dh+ 15fZc 2 + 3e 3 =0 
+ 13e 3 - 45c 2 /- 45c/ 2 -10/ 3 = 
-78/ 3 + 219/V + lll// + 13 /? 3 = 
&c. 



a = lb + c 
b=lc +d 
c ='M + e 
d=2e+f 

f = 3g + h 
&c. 



The equation in d and e gives the multipliers 

r = .S; £=£1.5; j»==1.5; 
while « = 5c?+2<? ; & = 3^+le ; hence for 1/5, we have the progression 

5 9.5 21.75 48.375 108.0375 241.14375 538.284375 



3' 5.5' 12.75' 28.275' 



63.1875 



141.01875 



314.791875 



&c. 



Here the error is reduced about 5 times at each successive step. 
The equation in e and f gives 






1 690 
13 3 



91 = 



585 
13 2 



45 



13 ' 



while a = 12* + 5/; 6 = 7^ + 3/. 

The progression thence resulting is 



12 



605 



34 245 1 915 230 107 241 125 



7 ' 354 ' 20 025 ' 1 120 045 ' 62 714 910 
converging more rapidly than the former. 



, &c, 



From these instances it is clear that the cube root of any number, or the 
root of any cubic equation with integer coefficients, may be represented by a 
series of chain-fractions of the third order ; and not by one only, but by many 
of such series. Since the successive steps of the Brounckerian process neces- 
sarily depends on the peculiarities of the case, it would be difficult to make a 
general analysis beyond the first step ; but a symbolical investigation that far 
may lead to important results. 

VOL. XXXII. PART II. 3 G 



320 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 

Let us take the general case of a number exceeding a perfect cube by, say, 
a ; that is a number of the form n 3 + a . We have here a = nb + c, and the 
equation 

a s -(n s + a)P=0 

becomes 

- ab 3 + 3n 2 bc + 3nbc 2 +c 3 =0 , 



which gives the multipliers 
or more conveniently 



- 1 ■ = 3 ' 1 - =^!i 2 

a a a 



a 2 3an 3n 2 

a 8 or a 



from which we have the elementary progression 

x 3n? 9?i 4 + 3cm 27n 6 +18g7i 3 + a 2 &Q 
a a 2 a 3 

and thence the progression of fractions 

cT_' 0_ 3ft, 3 + a 9n s + G a n 2 27 "n 6 + 27 an 3 + 4q 2 

.0 ' 3n 2 ' 9n* + 3 a n ' 27n 6 + 18an 3 + a? ' 

following exactly the law of those already found when the excess a is unit ; the 
multipliers being a 2 , 3an, 3?i 2 . 

By a proceeding exactly analogous to that formerly used, we find that the 
convergence to the cube root of the ratio n 3 — a : n 3 , is obtained from a progres- 
sion of which the multipliers are 

r = a 6 ; q=-3a i ; p = 27n e + 27 an* + 3a 2 , 

the initials being; 

+ q- 0. 3n 3 + 2a 
-a' 3 ' 0' 3n 3 + la' 

This formula may be generalised by substituting for n* any number K. Then 
lj 1 T a is obtained with the multipliers 

« 6 ; -3« 4 ; 27K 2 + 27aK + 3a 2 



from the initial terms 

-fa' 3 . 0. 3K + 2« 
-a" 3 ' 0' 3K + lo' 




CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 321 

3/L 
And again, if we write K + a = L or a = L— K, \J i? results, with the 

multipliers, 

(L-K)«; 3(L-K>; 3L 2 +21KL + 3K 2 ; 

from the initials 

+ (L-K- 3 . 0. K + 2L , 2K 3 + 30K 2 L+42KL 2 +7L 3 
-(L-K- 3 ' 0' 2K + L'' 7K 3 + 42K 2 L+30KL 2 +2L 3 ' 

These inquiries have been confined to the components of two terms 
only of the elementary progression, whereas in chain-fractions of the third 
order three terms are admissible. For the purpose then of giving the utmost 
generality to our research we shall suppose the three initial terms of a progres- 
sion to be 

ABC 

' ID ' ' 

a p y 

the multipliers being, as before, r, q, p. Then, according to what has been 
already shown, the /zth subsequent terms is 

[w-2]rB + [M-l]{rA + gB} + |>]C 
[n + 2]r/3 + [n-l]{ra + qp} + [n]y ' 

If then x be the asymptote of the elementary progression, while S is that of 
the series of fractions, we must have 

rB + (r A + qB)x + Gc 2 _ g , , 9 , 

and we wish now to express S directly in terms of the nine data, A, B, C ; a, 
fi> y ', P, q> r- For this purpose we must eliminate x from the two equations 
(1) and (2). 

Equation (2) may be written in the form 

(C-yS)x 2 +{r(A-aS) + q(B-/3S)}x+r(B-l38)=0 (2) 

from which and 

x 3 — px 2 — qx— r=0 (1) 

we have to eliminate x. The elimination gives 



322 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 

S3 1 y2 a 8 + 2qra 2 /3 +pr a 2 y + ( pr + cf) a ft 2 + (pq- 3r)a/3y - qay 2 + (pq + ^W 
+ (p 2 -qWy-2pPy* + y*} 
-S 2 {A[3r 2 a 2 + 4qra/3 + 2pray + (pr+q 2 )p 2 + (pq-or)/By-qy*] 

+ B[2qr a 2 + (2pr + 2 2 2 )a/3 + (pq - 3r)ay + (3pq + 3r)/3 2 + (2f - 2q)fiy - 2py*\ 
+ C[pra 2 + (pq-3r)a/3-2qay + (p 2 -q)/3 2 -4,p/3y + 3y 2 ]} 

+ S{a[3r 2 A 2 + 4:qrAB + 22}rAC + (q 2 +pr)'B 2 + (pq-3r)BC-qC 2 ] 

+ 8[2qrA 2 +(2pr+2q 2 )AB + (pq-3r)AC+(3pq + 3r)B 2 + (2p' i -2q)BC-2pC 2 ] 
+ y[prA 2 + (pq - 3r)AB -2qAC + (p 2 - q)B 2 - 4pBC + 3C 2 ] } 

- S°{?- 2 A 3 + 2qrA 2 B +pr A 2 C + (pr + q 2 )AB 2 + (pq - 3r) ABC - 9 AC 2 + (pq + r)B* + 

(p 2 -q)B*C-2pBC 2 + C*} = (3) 

Thus it appears that, while the root of every cubic equation may be reached 
by help of a recurring chain-fraction of the third order, every such fraction has 
for. its asymptote the root of a cubic. The above equation (3) gives us directly 
the form of the cubic when the initials and the scheme of progression are 
known ; and, inversely, it contains the means for discovering the progression 
suiting a proposed cubic. Thus for such an equation as 

GS 3 -HS 2 + KS-L=0, 

we must equate the above coefficients to G , H , K , L respectively. Here, 
among the nine unknowns, p , q , r ; A , B , C ; a , fi, y , we have only four 
conditions, so that we are at liberty to make five arbitrary assumptions. Now 
of the six, A, B, C; a, /3, y , the third power of each occurs ; hence the 
ultimate equation must contain at least one cube. Thus we are again thrown 
back on the solution of a cubic ; but in this case we know that it is always 
possible so to make the assumptions as that the root may be integer, provided 
the coefficients of the given equation be so. 

The preceding very involved expressions may be replaced by others con- 
siderably simpler. The nth. term of the progression may be written 

D[w] + E[n-l]+F[w-2] 
d[n] + e[n-l] + F[n-2] ' 

where D takes the place of rB , E that of (rA + qB) , and F that of C ; and 
similarly for the denominator. The asymptote then is 

whence 

(D~dS)a; 2 + (E cS)x-(Y-f)x=0 . 



CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 323 

The elimination now gives 

S3{ r s^3 _ qrd 2 e + ( g2 _ 2pr)d 2 f+prde 2 - (pq + 3r)dcf+ (p 2 + 2q)df 2 + re 3 - qe 2 f+pef 2 +/ 3 } 

- S 2 {3r 3 Dd 2 - qr(2T>de + Yd 2 ) + (q 2 - 2pr)(2Vdf+ Yd 2 ) +pr(J)e 2 + 2Yde) - (pq + 3r) 

(Def+ Ydf+ Yde) + (p 2 + 2q)(Df 2 + 2Ydf ) + 3rYe 2 - q(2Yef+ Ye 2 ) +p(Yf 2 + 2Yef) 
+ 3F/ 2 } 

+ S!{3r3D 2 d- qr(D 2 e + 2BYd) + {q 2 - 2pr)(D 2 f+ 2DYd) +pr(2BEe + Y 2 d) - (pq + 3r) 
(DE/+ DFe + YYd) + [p 2 + 2 2 )(2DF/+ Y 2 d) + 3rY 2 c - q(E 2 f+ 2YYe) +p 
(2EF/+F 2 e) + 3F 2 /} 

-S°{r 3 D 3 -jrD 2 E + (q 2 - 2pr)D 2 Y+prJ)Y 2 -(pq + 3r)DEF + (^ 2 + 2 ? )DF 2 + rE 3 - 2 E 2 F 
+ pEF 2 + F 3 } = (4) 

It may be interesting to apply this method to some problems in geometry ; 
and we may take the construction of the heptagon as a first example. 

The ratio of the diagonal to the side of a regular pentagon is given by the 
well-known series 0, 1, 1 , 1, 2, 3, 5, 8, 13, 21, &c, in which each term 
is the sum of the two preceding, this being a progression of the second order 
having the multipliers q = 1 , p — 1 . 

The relation between the long diagonal, a , and the side, b , of a heptagon 
is easily shown to be 

a*-2a 2 b-ab 2 + V = 0, 

which gives at once the multipliers r — 1, q—+l, p — 2, whence the pro- 
gression 

, , 1 , 2 , 5 , 11 , 25 , 56 , 126 , 283 , 636 , &c. , 

each new term being the double of the last found together with the difference 
between the preceding terms. The convergence here is slow ; to make it more 
rapid we may write a = 2b + c , and so get the equation 

-¥ + 3b 2 c + 4bc 2 + c 3 = 0. 
This gives the multipliers r = l , y = 4, p — 3 ; whence the progression 

1 2 7 29 117 474 & 
0' 0' 1' 3' 13' 52 ' 211' °" 



324 



EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF 



and a still more rapid convergence is obtained by putting b = 4:C + d; we then 

find 

c*-20c 2 d- 9cd 2 -(P=0, 
while 

a = 9c + 2d, b=4c + ld. 

Here r = l , q = $, p = 20, and the rapidly converging series is 

2 9 182 3 721 76 067 185 805 



1 ' ' 4' 



81 ' 1 656 ' 33 853 



82 691 



, &c. 



Enneagon. 

If we contract an isosceles triangle, having each angle at the base quadruple 
of the angle at the vertex, and if we lay off along the side two parts, each equal 
to the base, and from the vertex one part, the three measures overlap by a 
distance easily shown to be the fourth term of a continued proportion, of which 
the side and the base are the first and second terms. 

Hence, if a be the long diagonal of an enneagon, and b the side, 



or 



a 2 : b 2 : : b : 35 — a , 



a?-8a 2 b + W=0. 



This equation gives at once a series having r— — 1, q = 0, j9 = 3 for the 
multipliers, viz. — 

, , 1 , 3 , 9 , 26 , 75 , 216 , 622 , 1 791 , 5 157 , &c, 

which converges pretty rapidly to the ratio of the base to 
the long diagonal. Here, from thrice the term last found, 
we subtract the ante- penult, in order to get a new term ; 
that is, from thrice AB we subtract PN to obtain AF. 
From thrice AF we should subtract KB to get the 
long diagonal of an enneagon having FA for its side. 
and so on, the distances PN , KB, BA , AF being in 
continued proportion. 

The figures FMNP and FABK are evidently similar ; 
so if in the continued direction FB we measure from K, 
twice FB, to M', we shall obtain an enlarged edition of the 
figure FMNP. 

The convergence becomes more rapid if we put a = 3b 
— c, so as to get the equation 

I— 9S s c+6&c-c s =0. 





CUBIC EQUATIONS BY HELP OE RECURRING CHAIN-FRACTIONS. 325 
The multipliers r=l , q= — 6 , p — 9 thus found give the progression 
-1 3 26 216 1791 14 849 



' ' 1 ' 9 ' 75 ' 622 ' 5 157 
which contains each alternate term of the preceding. 



, &c, 



The construction of a regular polygon of eleven sides involves an equation 
of the fifth order, and would introduce chain-fractions also of that order. The 
extension of the present method to that case offers no difficulty, but would 
pass beyond the scope of this paper. 

In the preceding examples we have several times examined the progression 
formed by each third term of the series ; and in the last example we have 
noticed the progression of the alternate terms. This brings us to the general 
law, that the terms taken at equal intervals along a series of recurring chain- 
fractions form a series of the same kind. Thus [0] , [2] , [4] , [6] , &c, are 
connected by the law 

[n-4:]{r*} x[it-2]{2pr-q 2 } + [n]{pi + 2q} = [n-2] , 

the multipliers being 

R = r 2 , Q = 2pr-q*, F=p 2 + 2q. 

And, similarly each third term forms a progression according to the law 

[n-6]{rS} + [n-3]{q 3 -3pqr-3r 2 }-[n]{p^ + 3pq + 3r} = [n + 3], 

where 

E = r 3 ; Q = g2-3p2r-3r 2 ; F=p 5 + 3pq+3r . 

In the same way, for the terms four steps apart, we have 

R=-r 4 ; Q=-2p 2 r 2 + 42?2 2 r-2 4 + 42r 2 ; 
P =p* + Ap\ + Apr + 2g 2 . 

This law of recurrence extends to chain-fractions of all orders, and even to 
periodic continued fractions. Thus, in seeking the square root of 7 by the usual 
process, we get the successive quotients 2; 1, 1, 1, 4 ; 1, 1, 1, 4; &c, 
occurring in groups of four, and giving the converging fractions, 

2111441114 1 1 1 

1 2 3 5 8.3_7 45 82 127. 590 717 1307 2 024 
0' 1' 1' 2' 3' 14' 17' 31' 48' 223' 271' 494' 765' 



326 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS, ETC. 

-| q 1 9>r o 09J. 

If we select here the last term of each group as ^ , g- , -^ , -^ , &c, or the 

2 37 590 
first term as y, ^r, ^» &c, we form a progression with the multipliers q = 1 , 

^? = 16. Similarly, for the square root of 20, we get the quotients 4; 2, 8; 

2,8; &c, occurring in groups of two, the successive approximations being 

4 2 8 2 8 2 

1.4 9.76 161.1364 2 889 & in which the terms - £ ^ £889 &c 
' T' 2 ' 17 ' "36 ' "305 ' "64T ' ^ C '' m W ° S ' 2 ' 36 ' 646 ' <BC '' 

progress with the multipliers q = — 1 , _p = 1 8 . 

This circumstance greatly facilitates our investigations in quadratics ; thus 

if the indeterminate equation 

X*=7y*+1 

were proposed, we have at once the solution by seeking J7, and taking the 
last term of each group : thus 

x— 8, y= 3, 

x= 127, y= 48, 

«=2024 , ?/=rl765 , and so on. 

are the solutions. 

When the group of quotients consists of two terms a, 6, the order of 
recurrence is given by q— — 1 , p = a8 + 2. 

For a period with the three quotients a, (3 , y , we have q= + 1 , p = a fiy 
+ a + /3 + y. 

For one with the four, a , ft , y , 8 , we have q = — 1 , p — afiyS + (a + y) 
08 + S) + 2. 

The subject, however, is too extensive to be treated as an appendix to the 
present paper. 



( 327 ) 



XIX.— On Knots. Part II By Professor Tait. (Plate XLIV.) 

(Read 2nd June 1884. ) 

One main object of the present brief paper is to take advantage of the 
results obtained by Kirkman,* and thus to extend my census of distinct forms 
to knottiness of the 8th and 9th orders ; for the carrying out of which, by my 
own methods, I could not find time. But I employ the opportunity to give, in 
a more extended form than that in the short abstract in the Proceedings, some 
results connected with the general subject of knots, which were communi- 
cated to the Society on January 6, 1879, as well as others communicated at a 
later date, but not yet printed even in abstract. 

I. Census of S-Fold and of Q-Fold Knottiness. 

1. The method devised and employed by Kirkman is undoubtedly much 
less laborious than the thoroughly exhaustive process (depending on the 
Scheme) which was fully described and illustrated in my former paper f; but it 
shares, with the Partition method, which I described in § 21 of that paper and 
to which it has some resemblance, the disadvantage of being to a greater or less 
extent tentative. Not that the rules laid down, either in Kirkman's method or 
in my partition method, leave any room for mere guessing, but that they are too 
complex to be always completely kept in view. Thus we cannot be absolutely 
certain that by means of such processes we have obtained all the essentially 
different forms which the definition we employ comprehends. This is proved 
by the fact that, by the partition method, I detected certain omissions in 
Kirkman's list, which in their turn enabled him to discover others, all of which 
have now been corrected. And, on this ground, the present census may still 
err in defect, though such an error is now perhaps not very probable. 

On the other hand, the treatment to which I have subjected Kirkman's col- 
lection of forms, in order to group together all mere varieties or transformations 
of one special form, is undoubtedly still more tentative in its nature ; and 
thus, though I have grouped together many widely different but equivalent 
forms, I cannot be absolutely certain that all those groups are essentially 
different one from another. • 

Unfortunately these sources of possible error, though they tend (numeri- 
cally) in opposite directions, and might thus by chance compensate one another 

* Ante, p. 281. t On Knots, Trans. R.SE., 1876-7. 

VOL. XXXII. PART II. 3 H 



328 PROFESSOR TAIT ON KNOTS. 

so far as to make the assigned numbers of essentially different forms accurate, 
cannot in any other sense compensate. In other words, there may still be 
some fundamental forms omitted, while others may be retained in more than 
one group of their possible transformations. Both difficulties grow at a fear- 
fully rapid rate as we pass from one order of knottiness to the next above ; and 
thus I have thought it well to make the most I could of the valuable materials 
placed before me ; for the full study of 10-fold and 11-fold knottiness seems to 
be relegated to the somewhat distant future. 

2. The problem which Kirkman has attacked may, from the point of view 
which I adopt, be thus stated : — •" Form all the essentially distinct polgehdra * 
{whether solids, quasi-solids, or unsolids) which have three, four, &c, eight, or 
nine, four-edged solid angles." Thus, in his results, there is no fear of 
encountering two different projections of the same polyhedron; or, in the 
language of my former paper, no two of his results will give the same scheme. 
Thus there is no one which can be formed from another by the processes of § 5 
of my former paper. 

3. But, when a projection of a knot is viewed as a polyhedron, we necessarily 
lose sight of the changes which may be produced, by twisting, in the knot itself 
when formed of cord or wire ; a process which (without introducing nugatory 
crossings) may alter, often in many ways, the character of the corresponding 
polyhedron. This subject was treated in §§ 4, 11, 14, &c, of my former paper. 
But it is so essential in the present application that it is necessary to say some- 
thing more about it here. It would lead to great detail were I to discuss each 
example which has presented itself, especially in the 9-folds ; but they can all 
be seen in PI. XLIV., by comparing together two and two the various members 
of each of the groups. 

The following example, however, though one only of several possible trans- 
formations is given, is sufficiently general to show the whole bearing of the 
remark, so far at least as we at present require it. 




It is obvious that either figure may be converted into the other, by merely 
rotating through two right angles the part drawn in full lines, the dotted part 
of the cord being held fixed. Also, the numbers of corners or edges in the 
right and left handed meshes in these two figures are respectively as below :— 

* This word is objectionable, on many grounds, in the present connection. But a more suitable 
one docs not occur to me ; and the qualification (given in brackets) will prevent any misconception. 
Of course no projection of a true polyhedron can bo cut by a straight line in two points only. 



PROFESSOR TAIT ON KNOTS. 329 

55332 64332 

443322 an 433332. 

These numbers would necessarily be identical if the forms could be repre- 
sented by the same scheme. As will be seen by the list below, § 6, these are 
respectively the second, and the sixth, of the group of equivalent forms of 
number vin of the ninefold knots. (See Plate XLIV.) 

The characters of the various faces of the representative polyhedra (so far at 
least as the number of their sides is concerned) are widely different in the two 
cases. [Mr Kirkman objects to this process that it introduces twisting of the 
cord or tape itself. No doubt it does, or at least seems to do so, but the 
algebraic sum of all the twists thus introduced is always zero; i.e., by "iron- 
ing out " the tape in its new form, all this twist will be removed. I have often 
used a comparison very analogous to this, to give to students a notion of the 
nature of the kinematical explanation of the equal quantities of + and — elec- 
tricity, which are always produced by electrification. If the two ends of a 
stretched rope, along whose cylindrical surface a generating line is drawn, be 
fixed, and torsion be applied to the middle by means of a marlinspike passed 
through it at right angles, one-half of the generating line becomes a right- 
handed, the other an equal left-handed cork-screw. Thus the algebraic sum 
of the distortions is zero. And, in consequence, if the rope be untwistable 
(the Universal Flexure Joint of § 109 of Thomson and Tait's Natural Philosophy) 
and endless, the turning of the spike merely^ gives it rotation like that of a 
vortex-ring. Such considerations are of weighty import in many modern 
physical theories.] 

As will be seen, by an examination of the latter part of Plate XLIV., even 
among the forms of 9-fold knottiness there are several which are capable of 
more than one different changes of this kind. Some of these I may have failed 
to notice. But it is worthy of remark that the 8-folds seem, with two excep- 
tions, to resemble the 7-folds in having at most two distinct polyhedral forms 
for any one knot. 

4. Kirkman's results for knottiness 3, 4, 5, 6, 7, when bifilars and composites 
are excluded, agree exactly with those given in my former paper. I have 
figured these afresh in Plate XLIV., in the forms suggested by Kirkman's 
drawings, omitting only the single 6-fold, and the single 7-fold, which are com- 
posite knots. 

As will be seen in the Plate, where they are figured in groups, there are but 
18 simple forms of 8-fold knottiness. Besides these there are 3 not properly 
8-fold, being composite {i.e., made up of two separate knots on the same string) ; 
either two of the unique 4-fold, or a trefoil with one or other of the two 5-folds. 
These it was not thought necessary to figure, especially as they may present 
themselves in a variety of forms. 



330 PROFESSOR TAIT ON KNOTS. 

And the Plate also shows that there are .41 simple forms of 9-fold knotti- 
ness. Besides these, and not figured, there are 5 made up of two mere separate 
knots of lower orders, and one which is made up of three separate trefoils. 

5. Thus the distinct forms of each order, from the 3rd to the 9th inclusive, 
are in number 

1, 1, 2, 4, 8, 21, 47 ; 

or, if we exclude combinations of separate knots, 

1, 1, 2, 3, 7, 18, 41. 

The later and larger of the numbers in these series, however, would be con- 
siderably increased if we were to take account of arrangements of sign at the 
crossings, other than the alternate over and under which has been tacitly 
assumed; and which are, in certain cases, compatible with non-degradation of 
the order of knottiness. This raises a question of considerable difficulty, upon 
which I do not enter at present. Applications to one of the 8-folds and to one 
of the 9-folds will be found in my former paper, § 42 (1). 

Another interesting fact which appears from Plate XLIV. is, that there are 
six distinct amphicheiral forms of 8-fold knottiness : at least if we include one, 
not figured, which consists of two separate 4-folds ; in which case we must 
consider that there are two six-fold amphicheirals, the second being the com- 
bination of right and left handed trefoils, described in § 13 of my former paper. 
Thus the number of amphicheirals is, in the 4-fold, 6-fold, and 8-fold knots 
respectively, either 1, 2, 6, or (if we exclude composites), 1, 1, 5. All but two 
of these 8-fold amphicheirals were treated in my former paper, two having been 
separately figured, and the other being a mere common case of the general 
forms of § 47. 

Finally, as a curious addition to the paragraphs on the genesis of amphicheiral 
knots, given in my first paper, I mention the following, which is at once suggested 
by the amphicheiral 6 -fold : — Keeping one end of a string fixed, make a loop on 
the other ; pass the free end through it and across the fixed end ; pass the free 
end again through the external loop last made, then across the fixed end, 
and so on indefinitely. The second time the fixed end is reached we have 
the trefoil (if the alternate over and under be adhered to), the third time we 
have the amphicheiral 6-fold; and, generally, the nth time, a knot of 3(w-l) 
fold knottiness, which is amphicheiral if n is odd. Three of these were, inci- 
dentally, given in my former paper. 

But, reverting to the main object of my former paper, we now see that the 
distinctive forms of less than 10-fold knottiness are together more than sufficient 
(with their perversions, &c.) for the known elements, as on the Vortex Atom 
Theory. 

6. From the point of view of theory, as suggested in §§ 12, 21, of my 






PROFESSOR TAIT ON KNOTS. 



331 



former paper, it may be well to give here the partitions of 2n which correspond 
to true knots— for the values of n from 3 to 9 inclusive. The various parti- 
tions, subject to the proper conditions, are all given, in the order of the number 
of separate parts in each ; those which have a share in one or more of the true 
knots, as given in the Plate, are printed in larger type. 



n = 3 


n = 6 (contd.) 
42222 


71 = 8 (contd.) 

772 


n = 9 


n = $ (contd.) 


33 


99 


66222 


222 


33222 


763 


972 


65322 




222222 


754 


963 


64422 






664 


954 


64332 


n = 4 


w = 7 


655 


882 


63333 






8422 


873 


55422 






44 


77 


8332 


864 


55332 


422 


752 


7522 


855 


54432 


332 


743 


7432 


774 


54333 


2222 


662 


7333 


765 


44442 




653 


6622 


666 


44433 




644 


6532 


9522 


822222 


11 = 5 


554 


6442 


9432 


732222 




7322 


6433 


9333 


642222 




55 


6422 


5542 


8622 


633222 


532 


6332 


5533 


8532 


552222 


442 


5522 


5443 


8442 


543222 


433 


5432 


4444 


8433 


533322 


4222 


5333 


82222 


7722 


444222 


3322 


4442 


73222 


7632 


443322 


22222 


4433 


64222 


7542 


433332 




62222 


63322 


7533 


333333 




53222 


55222 


7443 


6222222 


n = 6 


44222 


54322 


6642 


5322222 




43322 


53332 


6633 


4422222 




66 


33332 


44422 


6552 


4332222 


642 


422222 


44332 


6543 


3333222 


633 


332222 


43333 


6444 


42222222 


552 


2222222 


622222 


5553 


33222222 


543 




532222 


5544 


222222222 


444 


11 = 8 


442222 


93222 




6222 




433222 


84222 










5322 


88 


333322 


83322 




4422 


862 


4222222 


75222 




4332 


853 


3322222 


74322 




3333 


844 


22222222 


73332 





The whole numbers of available partitions are thus in order : — 

2, 4, 7, 14, 23, 40, 66. 
Of these there are employed for knots proper only 

2, 1, 4, 4, 12, 17, 36, 

respectively. The remainder give links, or composite knots, or combinations 
of these. (See Appendix.) 

To enable the reader to identify, at a glance, any knot of less than 10-fold 
knottiness, I subjoin the partitions corresponding to each figure in Plate XLIV. 
It is to be remembered that (as in § 15 of my former paper) deformations which 
are compatible with the same scheme, however they may change the appearance 



332 



PROFESSOR TAIT ON KNOTS. 



of a knot, do not alter the partitions. But it is also to be remembered that 
identity of partitions, alone, does not necessarily secure identity of form. 
The 3, 4, 5, and 6-folds may be disposed of in a single line. 



33 
222 



71=4 

332 



w=5 

442 55 

3322 , 22222 



n=6 



4332 



543 
33222 



552 
33222 



Here the bar indicates not only that the right and left-handed partitions 
are alike in number and value, but also that they are similarly connected, i.e., 
that the knot is amphicheiral. 



I. 



5333 4433 
43322 or 43322 



For the Sevenfolds, we have 



II. 



5432 
43322 



or 



5432 
33332 



III. 



5432 

44222 



or 



4433 
44222 



IV. 



644 
332222 



5522 
44222 



VI. 


VII. 


662 


77 


332222 


2222222 



For the Eightfolds, 



I. 




II. 




III. 








54322 54322 
53332 or 44332 


54322 
or 43333 


53332 
44422 ' 


44332 


44332 


3r 44422 


IV. 


V. 




VI. 




VII. 


5443 


54322 
44332 




6532 
32 333322 


6532 
or 433222 




333322 


0r 54322 0r 443 


43333 


VIII. 




IX. 


X. 


XI. 




6433 
433222 


5443 
or 433222 


5542 
433222 


54322 54322 
44332 or 54322 


55222 
44332 


55222 
or 54322 


XII. 


XIII. 


XIV. XV. 


XVI. 


XVII. XVIII. 




6532 
433222 


655 763 754 
3322222 3322222 3322222 




772 


54322 


55222 


3322222 



I. 



4 I in:; 
133332 



Finally, for the Ninefolds, the list is 



II 



I. 

63333 63333 54333 54333 44433 44433 

533322 or 443322 or 533322 or 443322 or 533322 or 443322 




PROFESSOR TAIT ON KNOTS. 



333 



III. 

54333 



or 



44433 



443322 Ul 443322 



IV. 

54432 
533322 



54432 54432 54432 
or 533322 or 443322 or 443322 



V. 



44442 
443322 



VI 

64332 



55332 



64332 



443322 or 443322 or 443322 



VII. 

54432 



or 



54432 



433332 UL 433332 



VIII. 

64332 55332 64332 55332 55332 64332 
443322 or 443322 or 533322 or 533322 or 433332 or 433332 



IX. 



54432 
443322 



X. 



5553 
3333222 



XL XII. 

5544 64422 64422 64422 64422 
3333222 433332 or 333333 or 533322 or 443322 



XIII. 

55422 



55422 



55422 



443322 or 533322 or 433332 



XIV. 

65322 65322 65322 65322 
433332 or 433332 or 533322 or 443322 



XV. 

65322 



55332 



55332 



65322 



443322 or 443322 or 543222 or 543222 



XVI. 

7632 



7632 



7632 



3333222 or 3333222 or 4332222 



XVII. 

64332 64332 54432 54432 
533322 or 443322 or 533322 or 443322 



XVIII. 

64332 



54333 



54432 



543222 or 543222 or 543222 



XIX. 

55422 
533322 



or 



55422 
443322 



XX. 

55332 



54432 54432 
543222 or 543222 or 543222 



XXI. 

7443 



XXII. 

7533 



6633 



7533 



6633 



7443 6543 6543 
4332222 or 3333222 or 3333222 or 4332222 4332222 or 4332222 or 3333222 or 3333222 



XXIII. 

6543 



or 



5553 



XXIV. 

6552 



XXV. 



4332222 Ui 4332222 



or 



6552 



4332222 U1 3333222 



64422 44442 44442 64422 
443322 or 543222 or 443322 or 543222 



XXVI. 

66222 66222 66222 

443322 or 543222 or 443322 



XXVII. 

5544 



or 



6543 



XXVIII. 

7533 



4422222 U1 4422222 



or 



6543 



4332222 U1 4332222 



XXIX. 

64422 



or 



64422 



XXX. 

7542 



543222 U1 443322 



or 



7542 



4332222 U1 3333222 



XXXI. 

65322 55332 

543222 or 543222 



334 PROFESSOR TAIT ON KNOTS. 

XXXII. XXXIII. XXXIV. XXXV. 

44442 64422 7632 6633 7542 5544 44433 
552222 or 552222 4422222 or 4422222 4422222 or 4422222 333333 

.XXXVI. XXXVII. XXXVIII. XXXIX. XL. XLI. 

666 864 882 66222 7722 99 

33222222 33222222 33222222 552222 4422222 222222222 

It will be seen that the above list suggests many curious remarks. Thus, 
in the eightfolds, we have two different amphicheirals, each having the parti- 

54322 



tions 44332. Again, we have p^o^o f° r a knot which is not amphicheiral, 

as well as 54322 for one which is amphicheiral. (See § 47 of my former paper.) 

54322 
And we have 44000 standing for two quite distinct knots. All these apparent 

difficulties, however, are due to the incompleteness of the definition by parti- 
tions merely {i.e., as by Listing's Type-Symbol). For, in addition to this, it is 
requisite that we should know the relative grouping of the right-handed or of 
the left-handed partitions. 

In the Plate I have inserted the designations given in my former paper to 
the various forms of 6-fold and 7-fold knottiness : — and I have also appended to 
each form the designation of the corresponding figure in Kirkman's drawings. 

The Plate contains a great deal of information of a kind not yet alluded to 
in this paper. It gives, for instance, an excellent set of examples of Knot- 
fulness. This term implies (§ 35 of my former paper) " the number of knots of 
lower orders [whether interlinked or not) of which a given knot is built up." It is 
to be understood as applied to simple forms only ; for we have set aside, as 
composite knots, all such as have any one component separable, so that it may 
be drawn tight without fastening together two laps belonging to one or two of 
the other components. 

Thus, as a few of the examples of 2-fold knotfulness among the 8-folds, we 
have 

vi. and xi. (3-fold and once-beknotted 5-fold) ; 
and 11. and v. (each two 4-folds) ; while 

in., ix., and xiv. are different forms of two (linked) 3-folds. 

Among the 9-folds we have, for instance, 

xxx. and xxxin. (4-fold and clear-coiled 5-fold), 
xvi. and xxvi. (3-fold and 8 6-fold), 

xiv., xv., xvin., and xxv. (4-fold and once-beknotted 5-fold). 
But we have also 

iv., xiii., xxiii., and xxiv. (linked 3-fold and 4-fold), 
xx., xxvii. (two 3-folds, linked, and with one kink). 



PROFESSOR TAIT ON KNOTS. 335 

The analysis of self-locked knots, such as iv. and vit. of the 8-folds, and n., ix., 
x., xix., &c, of the 9-folds, is considered below. 



II. Beknottedness. 

7. The question of Beknottedness (on which I have occasionally made short 
communications to the Society since my papers of 1876-7 were printed in a 
brief condensed form) has been again forcibly impressed on me while 
endeavouring to recognise identities among Kirkman's groups. I still con- 
sider that its proper measure is the smallest number of changes of sign which 
will remove all knottiness. But, shortly after my former paper was published, I 
was led to modify some ideas on the subject, which were at least partially 
given there. I had been so much impressed by the very singular fact of the 
existence of amphicheiral forms, that I fancied their properties might in great 
measure explain the inherent difficulties of this part of the subject. I have 
since come to see that this notion was to some extent based on an imperfect 
analogy, due to the properties of the 4-fold amphicheiral, and that the true 
difficulty is connected with Locking. 

8. The existence and nature of this third method of entangling cords were 
first made clear to me by one of the random, sketches which I drew to 
illustrate Sir W. Thomson's paper on Vorte.x- Motion [Trans. R. S. E., 1867-8]. 
I had not then even imagined that the crossings in any knot or linkage could 
always be taken alternately over and under, though I found that I could make 
them so in all these sketches. The particular figure above referred to again 
presented itself, among others possessing a similar character, while I was 
studying the peculiar group of plaited knots whose schemes contain the lettering 
n alphabetical order in the even as well as in the odd places. (See §§ 27, 42, 
of my former paper.) But I soon saw that, though I had first detected locking 
in those members of the group of plaits where three separate strings are 
involved, essentially the same sort of thing occurs in the other members of the 
group, though they are also proper knots in the sense of being each formed 




with a single continuous and endless string. And, as the above very simple 
example sufficiently shows, we can have locking, independent of either knotting 
or linking, with two separate strings. For it is clear that the irreducibility 

VOL. XXXII. PART II. 3 I 



:530 PROFESSOR TAIT ON KNOTS. 

of this combination depends solely upon the sign of the central crossing. 
There is no real linking of the two cords, and there is obviously no knotting. 
But if the sign of any one of the crossings, except the central one, be changed, 
the whole becomes the simple amphicheiral link, the linking having been 
Introduced by the change of sign. [This, as will be seen in § 14 below, is an 
excellent example of a case in which the key-crossing of a locking is also a 
root-crossing of a fundamental loop.] 

9. We may therefore define, as one degree of locking, any arrangement, or 
independent part of an arrangement, analogous to that above (whether it be 
made of one, two, or three separate strings), the criterion being that the change 
of one sign unlocks the whole. But it is well to notice, again, that if, in the 
above figure, we change the sign of any crossing except the central one, we 
have one degree of linking left, and that this has in reality been introduced by 
the change of sign. This remark extends, with few exceptions, to more 
complex cases. 

- 10. Thus, though the following 8-fold knot (which I reproduce from 
Trans. R. S. E., 1877, p. 188) does not, at first sight, appear to depend on 




locking, we have only to make a simple transformation (as ante, § 3) to re- 
duce it to the symmetrical form in which the single degree of locking is 




at once evident. It was by considering this knot, with its (quite unex- 
pected) single degree of beknottedness, that I first saw the true bearing 
of locking in the present subject. (It is given as x. of the 8-folds in Plate 
XLIV.) 

Other excellent instances of the same difficulty are the following. The first 
of these is completely resolved, the second changed to the 3-fold, while the third 
becomes apparently two linked trefoils, all by the change of the single crossing 
in the middle of the lock. But with the 9-fold knot (which is merely a different 



PROFESSOR TAIT ON KNOTS. 337 

projection of PL XLIV. fig. xxxv.) the trefoils are so linked after this 
operation, that the change of sign of one crossing of either resolves the whole. 






This is, however, much more easily seen by at once changing the signs of the 
middle and of the lower (or the upper) crossing, for the whole is thus resolved. 
[This course is at once pointed out by the process of § 13 below, if we choose 
as fundamental crossings the three highest in the figure.] Hence the beknotted- 
ness is 1, 2, 2 in the last three figures respectively. 

11. Another instructive example is afforded by the 8-fold knot below, 
which is figured as iv. on Plate XLIV. : — ■ 




At a first glance it appears to be made of two once-linked trefoils, and there- 
fore to have three degrees of beknottedness. But a little consideration shows 
that neither the trefoils nor the link have alternations of signs (i.e., there is 
neither knotting nor linking), but that the whole is kept from resolution solely 
by the lap of cord which has been drawn as a straight line in the figure. This 
forms, as it were, the tail of a Rupert's drop ; break it, and the whole falls to 
pieces. A change of sign of either of the interior crossings on that lap makes 
one trefoil ; of either of the 4 lateral external crossings, the 6-fold amphi- 
cheiral ; of the upper crossing, the 4-fold amphicheiral ; and of the lower axial 
crossing, the 5-fold of one degree of beknottedness. All these modes of resolu- 
tion lead to the result that the knot is of 2-fold beknottedness. 

12. It is now obvious why, in consequence of locking and not of amphi- 
cheiralism as I first thought, the electro-magnetic test fails in certain classes of 
cases to indicate properly the amount of beknottedness. For it is clear that 
in pure locking there is no electro-magnetic work along the locked part of any 
one of the three courses involved. Hence, for the part of a knot or link which 
is locked, the electro-magnetic test necessarily gives an incorrect indication of 
beknottedness. Perhaps it may be said that, in such cases, beknottedness is 
not the proper name for this numerical feature of a knot: — but it is obviously 
correct if defined as in § 7 above. 



338 PROFESSOR TAIT ON KNOTS. 

13. A simple but thoroughly practical improvement on the methods given 
in my first paper for the graphical solution of Gauss' problem (extended) is as 
follows : — Draw the knot or link, as below, with a double line, like the edges 
of an untwisted tape, and dot (or go over with a coloured crayon) one of the 




two lines. Now it is easy to see that, of the four angles at a crossing, one 
angle is bounded by full lines, and its vertical angle by dotted lines. These 
will be called the symmetrical angles. Also it is clear that the electro-magnetic 
work has one sign for the crossings when the symmetrical angles are right- 
handed, and the opposite sign when they are left-handed. Thus we can at once 
mark each crossing as r or /, silver or copper, at pleasure. If the figure be a 
knot, and if we cut it along a line dividing a symmetrical angle, re-uniting the 
pairs of ends on either side of that line, the whole remains a knot (still with 
alternations of over and under if the original was so), but of knottiness at least 
one degree lower. When the line divides an unsymmetrical angle, the whole 
becomes (after re-uniting the ends, as before) two separate closed curves, in 
general linked and, it may be, individually knotted. [When we treat a link in 
this way at any of the linkings (i.e., where two different strings cross one 
another), it becomes a knot. It is curious that by this process a knot is 
equally likely to be changed into a knot or into a link, while a link always 
becomes a knot.] This method has the farther advantage of showing at 
a glance the various sets of crossings which we may choose for omission 
(in the electro-magnetic reckoning), as due merely to the coiling of the figure, 
not to knotting, linking, or locking. For each such crossing must belong to a 
simple loop, which, for reference, we will call fundamental. Such a loop is 
detected immediately by its having (throughout) the full line or the dotted line 
for its external boundary, and therefore is necessarily closed at a symmetrical 
angle. If we now erase these fundamental loops in succession, till no crossings 
are left, the crossings at their bases form one of the groups which may be tried. 
When part of the knot has locking, it is sometimes necessary to try more than 
one of these groups before we arrive at the true measure of beknottedness. 
As this is a matter of importance, it may be well to discuss it a little farther. 

14. When there is no beknottedness (whether true, or depending on linking 
or locking), the electro-magnetic work, with the proper correction for mere 
coiling, is certainly nil. But this proper correction requires to be found, and 
where there is locking its discovery sometimes presents a little difficulty. 
When there is no locking, all we need do is to draw the knot afresh, beginning 




PROFESSOR TA1T ON KNOTS. 339 

at a point external to each of the fundamental loops, and making each crossing 
positive when ive first reach it. It is evident that the fundamental loops or 
coils will now be simply laid on one another. The signs of all the crossings on 
any one loop may be changed, while that of the base of the loop is immaterial, 
and this process may be carried out with some or all of the other fundamental 
loops in any order. Compare the various signs in any state thus produced 
with those (alternate or not) of the original knot, so as to find the smallest 
number of changes necessary for its full resolution. The sign of the crossing 
at the base of each fundamental loop is simply to be disregarded. Another 
mode of going to work is to alter the signs at pairs of points where two funda- 
mental loops cross, so as to diminish as far as possible the necessary number of 
real changes of sign. But we must be very careful in using this process, to see 
that it does not introduce locking. 

15. When there is locking in part of the knot, the real difficulty is met with 
only if the crossing or crossings which form as it were the key of the locked 
part, must also be taken as the base or bases of fundamental loops. In this 
case we commence the fresh drawing of the knot at a point exterior to the 
locking, but on the fundamental loop of which one of the key crossings forms 
the base. This ensures that the completion of the fundamental loop is effected 
by the last of the operations on the locked part. But the application of the 
method can be learned far more easily from an example or two than from any 
rules which could be laid down. Thus the following drawings represent the 
results of this method as applied to two of the knots already figured. In the 





first of these the two lower external crossings are taken for the fundamental 
loops, and we see that the knot (if originally over and under alternately) re- 
quires for its full resolution only the change of sign of each of the two cross- 
ings which lie in its axis of symmetry. But, if we had chosen the crossings 
last mentioned as bases of fundamental loops, we should at once have felt the 
difficulty due to locking. 

In the second, all four crossings in the axis of symmetry close fundamental 
loops ; but the change of the sign of the lowest of these, alone (which is the 
key of the locked part), is required for the full resolution. 



340 PROFESSOR TAIT ON KNOTS. 



APPENDIX 



Note on a Problem in Partitions. By Professor Tait. 

(Read July 7, 1884.) 

In the partition method of constructing knots of any order, n, of knottiness, we have to select from 
the group of partitions of 2n those only in which no part is greater than n, and no part less than 2. 

Thus, as given in the text, § 6, we have for sevenfold knottiness the series of partitions of 14; — 
but they are now arranged below in classes according to the value of tbe largest partition. 



77 


662 


554 


4442 


33332 


2222222 


752 


653 


5522 


4433 


332222 




743 


644 


5432 


44222 






7322 


6422 


5333 


43322 








6332 


53222 


422222 








62222 











It is an interesting inquiry to find how many there are in each class, for any value of n. The number 
of classes is obviously n - 1 ; and, if we remove from each the first partition (i.e., that which is not in- 
ferior to any of the others), the remainders form a new set of classes of partitions which we may desig- 
nate as 

Pn > Pu+1 1 Pn+2 ) • • ■ P'ln-1 

respectively; — where p\ is defined as the number of partitions of s, in which no partition is greater than 
r, and none less than 2. 

Without explicitly introducing finite differences or generating functions it is easy to calculate the 
values of the quantity p\; — and to put them in a table of double entry which can be developed to any 
desired extent by the simplest arithmetical processes. The method is similar to one which I employed 
some years ago for the solution of a problem in Arrangements (Proc. R.S.U., viii. 37, 1872). 

In the first place we see at once that if r>s 

V\ =p\ ■ 

Thus, if r denote the column, and s the row, of the table in which p T , occurs, all numbers in the row 
following p\ are equal to it. Thus the values of p\ enable us to fill up half the table. In the remain- 
ing half r is less than s ; and by a dissection of this class of partitions, similar to that which was given 
above, we see that 

l>: =l?.- r +P r .:ln+ • • ■ ■+P i ,-2+pl-i-^P°., 

where the two last terms obviously vanish ; and the first term is obviously 1 in the case of r = s, uni 
r<2, when it vanishes. 




> 



+ 


+ 


+ 


+ 


+ 


+ 


+ 


II 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


G 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


F 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


E 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


I) 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


C 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


B 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


A 


+ 


+ 


+ 


K 


+ 


+ 


L 


L 



PROFESSOR TAIT ON KNOTS. 341 

Hence, if the following be a portion of the table, the crosses being placed for the various values of 
p T ,, nil or not, 

Values of r. 
012345678 



1 

«(-! 2 

o 

03 3 

4 

5 

6 

7 

it will be seen at a glance that the above equation tells us to add the numbers A, B, C, D, E together 
to find the number at K. This is quite general, so that L, in the second last column, is the sum of 
A, B, . . . . , H ; and all the numbers beyond it, in the same row, are equal to it. In the table on next 
page, each number corresponding to the first L is printed in heavier type, and its repetitions are taken 
for granted. 

Thus it is clear that simple addition will enable us to construct the table, row by row, provided we 
know the numbers in the first row and those in the first column. Those in the first and second columns 
are all obviously zero, as above. The rest of the first row consists of units. These are the values of 
p r , i.e., the first term of the expression above for p T r . Hence we haVe the table on the following page, 
which is completed only to r = 17, with the corresponding sub-groups. 

Erom the table we see that p\ = 8. Hence the partitions of 18, subject to the conditions, are in 
number 

8 + 11 + 11 + 14 + 10 + 8 + 3 + 1 = 66, 

which agrees with the detailed list in § 7 above. 

[The rule is to look out the number p" n , and add it to all those which lie in the diagonal line drawn 
form it downwards towards the left. But the construction of the table shows us that this is the same 
as to look out p? n at once.] 

Similarly we verify the other numbers of partitions given in the text. 

And it is to be remembered that p£ is the number of required partitions in which n occurs, and that 
every one of the class p"^. has for its largest constituent n - r. Thus, looking in the table for p] and 
the numbers in the corresponding downward left-handed diagonal, we find the series 

4 6 5 5 2 1, 

which will be seen at once to represent the dissection of the partitions of 1 4 given above. 

The investigation above was limited by the restriction, imposed by the theory of knots, that no par- 
tition should be less than 2. But it is obvious that the method of this note is applicable to partitions, 
whether unrestricted, or with other restrictions than that above. The only difficulty lies in the border- 
ing of the table of double-entry. Thus, if we wish to include unit partitions, all we have to do is to put 
unit instead of zero at the place r= 1, s = 0, and develop as before. Or, what will come to the same 
thing, sum all the columns of the above table downwards from the top, and write each partial sum 
instead of the last quantity added, putting unit at every place in the second column. 

Similarly, we may easily form the corresponding tables when it is required that the partitions shall 
be all even, or all odd. 



342 



PROFESSOR TAIT ON KNOTS. 



Table of the values of p* ; the number of partitions of s in which no one is 
less than 2, nor greater than r. 

{The values of v are in the first row, those of s in the first column.) 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 












1 
























1 










. 


. 




















2 








1 


. 


. 




. 
















3 











1 






. 
















4 








1 


1 


2 




. 
















5 











1 


1 


2 


. 
















6 








1 


2 


3 


3 


4 
















7 











1 


2 


3 


3 


4 














8 








1 


2 


4 


5 


6 


6 


7 












9 











2 


3 


5 


6 


7 


7 


8 










10 








1 


2 


5 


7 


9 


10 


11 


11 


12 








11 











2 


4 


7 


9 


11 


12 


13 


13 


14 






12 








1 


3 


7 


10 


14 


16 


18 


19 


20 : 


20 : 


21 . 




13 











2 


5 


10 


13 


17 


19 


21 


22 


23 


23 24 . 




14 








1 


3 


8 


13 


19 


23 


27 


29 


3i : 


52 : 


33 33 34 . 




15 











3 


7 


14 


20 


26 


30 


34 


36 


38 


39 40 40 41 




16 








1 


3 


10 


17 


26 


33 


40 


44 


48 50 52 53 54 54 55 . 


17 











3 


8 


18 


27 


37 


44 


51 


55 59 61 63 64 65 65 6 


18 








1 


4 


12 


22 


36 


47 


58 


66 


73 77 81 83 85 86 87 . 


19 











3 


10 


23 


36 


52 


64 


75 


83 90 94 98 100 102 




20 








1 


4 


14 


28 


47 


64 


82 


95 


107 115 122 126 130 . 




21 











4 


12 


29 


49 


72 


91 


110 


123 135 143 150 . 




22 








1 


4 


16 


34 


60 


86 


113 


134 


154 168 180 . 




23 











4 


14 


36 


63 


96 


126 


155 


177 197 . 






24 








1 


5 


19 


42 


78 


115 


155 


189 


220 








25 











4 


16 


44 


80 


127 


171 


215 










26 








1 


5 


21 


50 


97 


149 


207 












27 











5 


19 


53 


102 


166 














28 








1 


5 


24 


60 


120 
















29 











5 


21 


63 


. 


. 














30 








1 


6 


27 


. 




. 




. 










31 











5 


. 


. 




. 




. 










32 








1 


• 


• 


• 


• 


• 




• 


• 









From what has been stated in the previous pages, it is easy to see how to 
extend this table ; forming the successive terms of each row by adding step by 
step upwards to the right along a diagonal, thence upwards to the top, zig-zag 
along the row of heavier type as soon as it is reached. 




Roy. Soc Edin* 

Ampin obi 



THE FIRST SEVEN ORDERS OF KN0TT1NESS. 

AmphicW I Two forms 



) 






Vol. XXXII, Pl.XL IV. 

II Two forms 




4- A sB sC (3 sA y GF 5 6 G II, vC 

orms IV Unique V Unique VI Unique VII Unique I Un Amphidi 1 II Three forms 



IV, ?D V, vE 

III Two forms 




III, ?G 

IV Unique 



VI, ?P X, rS IX, vT Vin, 7U XI, ?V 8B 

ms,the2^t3'>AmpHdii VI Two forms VII Un Amph. VIII Two forms 




E 8G 

IX Unique 



8X 8F 8Q 8T 

X Two forms XI Two forms 




8 L 8 Am 8 Ac 8 Av 8 Aj> 8 At 8 Au 8 A z 

phicB XIII Unique XIV Unique XV Unique XVMJmgue XVH Un Amphl XVjniWie I Unique 



8 B"b 8 Ax 

II Six forms 



Bg 8 Bl 




P.tlulh.UFEirf 






7'. ■%-'L> t'i 






( 343 ) 



XX. — Philosophy of Language. By Emeritus Professor J. S. Blackie. 

(Eead 7th April 1884.) 

The Universe, as we have it, is an organised system of rational or reasonable 
forces and forms ; of which the former are the product of the plastic, self- 
energising, productive power within, the latter the external presentation or 
manifestation of that power. 

I. Language is a form of the fluid element, the air, moulded into shape by the 
vital forces of any living creature acting under the constraint of a determined 
organism, and significant of the sensations, emotions, sentiments, or thoughts of 
the creature; transmitted to and made appreciable to other similarly consti- 
tuted creatures by the instrumentality of the ear, an organ nicely sensitive to 
all the affections of the fluid element, and thus naturally fitted to be the 
medium of intelligible communication between creature and creature in a 
system of social interdependence. 

II. The simplest elements of language which we have in common with the 
lower animals are of the nature of cries ejaculated or instinctively sent forth 
from the vocal organs of the creature, under the stimulus of some sensations of 
pain or pleasure, either arising altogether from within, or called into action by 
some external agency, as the pricking of a pin, — such cries as the cawing of 
rooks, the purring of cats, the grunting of pigs, the braying of asses, the cackling 
of geese, the shrieking of women, and the roaring of men, — cries which arise 
necessarily from the nervous constitution and vocal organism of the creature, 
and which are naturally intelligible to all creatures of a kindred nature, and 
endowed with a responsive susceptibility. These cries in human language 
are, in the language of grammar, interjections : such as ha, ha ! ho, ho ! £> poi, 
fiafiaL But they are in fact verbs, or at least the soul of a certain class 
of verbs, performing, as a means of communication between creature and 
creature, the complete function of verbs, and becoming perfect verbs in 
grammatical form directly they are tied down by certain modifications to 
definite relations of personality and time ; of which anon. 

III. Were a human being only a bundle of sensibilities, human language would 
consist merely of such ejaculatory words; but this sensibility is only the starting 
point of his existence, the point which he has in common with a mouse, a midge, 
or a monkey ; he soon becomes a perceptive animal, and after that a mimetic or 
imitative animal ; being moved by an unfailing instinct to reproduce, in some 
form or other, whatever striking forms or energising forces from without may 

VOL. XXXII. PAET II. 3 K 



344 EMERITUS PROFESSOR J. S. BLACKIE ON 

have strongly affected his nature. Hence, the whole family of words, in 
grammars stupidly called onomato-poetic, in which we recognise the germ of the 
dramatic element in literature, as in the ejaculatory element we may recognise 
the germ of the lyrical element. This whole class of words, representing 
originally all sorts of natural sounds, is manifestly the product of the native 
dramatic instinct of the human creature, and, though starting originally from im- 
pressions of sound, readily adapts itself by analogy to cognate impressions of the 
other senses, and even to emotions of the mind, and in this way claims a much 
larger domain in the field of every cultivated speech than would at first sight seem 
to belong to it. 

IV. Our next proposition brings us to a higher and a characteristically 
human platform. When I call an ox, bo — bov — baa, as in Greek, Latin, and 
Gaelic, this, as a mere echo of an animal sound, might be repeated by a parrot, 
or any other animal with imitative instinct and apt vocal organisation. But 
the moment I use this imitative sound to express the name, not only of the indi- 
vidual animal which I just heard utter the sound, but the notion, idea, or type of 
a whole class of animals uttering the sound, I plant myself on a platform of in- 
tellect of which no animal, not even the cleverest monkey, is capable. The 
genesis of the idea in the human soul is a matter of which neither sensation nor 
sensibility can give any account ; sensation is always the occasion, never 
the cause, of the idea. Four eggs, for instance, are no doubt felt to be four by 
a dog, or bull, or by a man ; but the leap from that to the mathematical 
proposition, 2 + 2 = 4, is infinite, and cannot be overbridged by any ingenuity. 
In forming the idea of an ox or a cow, the vovs or Xdyos, which differentiates a 
man from a brute, acts plastically from its own dominant centre, and uses 
sensuous impressions merely as a multiform material on which the unity of an 
intelligent type is impressed; here we have the birth of human, that is intellec- 
tual language, a language expressive, not of sensations or of feelings, but of 
thoughts and ideas, which are as general as mathematical definitions, and are the 
pure creations of thinking. In forming them man acts as a god creating an 
organism ; and this truth, so habitually ignored by a certain narrow school of 
physical scientists in these latter days, is not the least striking manifestation of 
the philosophic depth which lies at the bottom of that text — Gen. i. 27, " God 
made man in his own image." Here we see distinctly the reason why brutes 
have no language in the sense that we talk of human language. The vital 
forces which belong to them, being purely of sensational and emotional origin, 
are satisfied by the lowest form of vocal expression which we call cries ; their 
language is in the main ejaculatory, and in some part also imitative. But 
there being no X0705 or vovs in them that craves for expressing in intelligible 
I' >rm, the words significant of types and general ideas, of course no such form 
appears ; and man stands emphatically differentiated from them as the only 



THE PHILOSOPHY OF LANGUAGE. 345 

speaking, because the alone thinking animal ; the Xoyos of speech being in part 
only the outside of the \6yos of thought, and both expressed significantly in 
Greek by the same word. We say, therefore, distinctly that the mass of 
human language consists of an array of articulated sounds elevated by the 
power of self-acting imperial mind — )3ao-iWos vovs, as Plato calls it — from their 
original sensous significance into the region of thought, and made thus 
to serve as an organ of thinking in the communications of a specifically 
thinking animal. 

V. That the vovs in the formation of language acts in its own imperial style, 
and not at all in the manner of Locke's unhappy simile of the sheet of blank 
paper, will appear plainly on considering the nature of that class of words 
which, in all languages, is found to express purely mental operations. They 
are, of course, formed by a secondary application of originally sensuous 
terms ; but the point lies not in their origin, but in the selection made from 
a host of words of the same origin. Thus, in Greek — KaraXa/x/Scww, o-witj/ai, 
crvk\oyit,(x) ; in Latin — comprehendo, concipio, intelligo ; in German — -J'assen, 
begreifen, plainly imply a very distinctly energetic forthputting of the 
internal moulding faculty to lay hold of the material presented by the 
senses, as a potter lays hold of the clay. And in this regard it is not without 
interest to remark that, whereas verbs of sensation generally in Greek govern 
the genitive case, verbs of seeing, which is pre-eminently the intellectual sense, 
always govern the accusative ; for the same reason evidently that active verbs 
generally govern that case, viz., because the accusative is a case of motion 
towards a point ; that is the appropriate case to mark the invasion, so to speak, 
of the external material world, by the internal vital force of the observer in the 
act of cognition. 

VI. The steps by which language grows from the original simple elements 
into the luxuriant expanse of significant sounds found in our dictionaries is not 
difficult to trace. The original stock, either in its single nakedness or with 
some modifications and slight additions, is adapted to new and very diverse 
uses by the law of similitude acting along with the law of parsimony. The law 
of parsimony, or a wise economy and a wise laziness, forbids to invent absolutely 
new words when old ones can serve the purpose ; and the law of similitude, 
which the mind constantly follows in the classifications of science, as in the 
inspirations of poetry, by easy steps of transference, leads to an unlimited 
variety of uses of the same root, just as in the world of colour dark green may 
pass into light yellow. The changes of meaning which the root undergoes in 
this process of adaptation to new objects and new circumstances are always 
instructive and often amusing. We shall content ourselves with two familiar 
examples. The word prick, for instance, whether as a noun or a verb, is, I have 
no doubt, derived from the slight sharp sound made by a pin or a drop of rain 



:J4(J emeritus professor j. s. blackie on 

falling on a dry surface. The various forms which it has assumed in its passage 
through the millions of millions of human mouths during long centuries, from 
Sanscrit, through all the Teutonic languages, will be found in Skeat. They all 
signify a dot or spot, or the point that makes it, or the act of making it ; and 
the last of the large progeny of small dots or points is one which is said to be 
produced either by native virtue of the academic soil at Oxford, or, as Lord 
Reay had it, by a peculiar metamorphosis which the rude unkempt Scot some- 
times undergoes when he is transplanted to that atmosphere compounded 
curiously of the four elements of Greek, Episcopacy, Aristocracy, and Plutocracy ; 
so that, to use the language of geologists, a prig is a metamorphic Scot, having 
in West End estimation the same relation to a normal Scot that a dainty 
Alderney cow has to a shaggy Highland stirk. This is the bright side of the 
creature, and the side of course from which he habitually contemplates himself. 
The dark side is revealed by the etymology which plainly sets him forth as a 
creature of small points and proprieties — a creature mighty in small matters — 
a sort of dainty drawing-room pedant — in whom the to o-e^vov of true manhood 
has been altogether swallowed by the to -rrpeirov of smooth convention, and the 
to KOfxxfjbv of petty elegance and superficial polish. Opposed to him is the 
sumph, a creature with neither points nor polish, from the German sump/, a bog, 
cro[x(f)6<;, porose, a Jop^jz-brainecl animal, whose depth, when he has any, is only 
a profundity of soft and sinking stupidity. Take now the word bull — not the 
animal which is kin to Bo, but the Pope's bull, which has nothing to do with 
the bovine cousinship in which the model Englishman glories. The Latin 
bulla, as every schoolboy knows, was a sort of boss or knob hung round the neck 
of patrician boys, and pet lambs sometimes, by fond Romish mamas ; its original 
meaning was a bubble of water, from bullio, English boil. This round boss or 
knob, in a leaden avatar, came in the Middle Ages to be attached, as a sort of 
seal or stamp, to the thundering ordinances which his Holiness of the seven hills 
used to thunder over Europe largely, in order to crush kings and frighten fools ; 
hence transferred to the document itself; and as the good old gentleman, with 
all his infallibility, sometimes blundered, a bull came to signify a blunder ; and 
as Irishmen are famous for blunders, the little gilded ornament on the baby 
patrician's neck became metamorphosed into a blunder very closely akin to the 
bubble out of which the word arose. 

VII. The modifications, in verbal form, which the root underwent, in order 
to adapt itself to new applications and to acquire new shades of meaning form 
two classes — those of which the origin and significance are either perfectly 
plain or can reasonably be presumed, and those of which the significance is 
altogether unknown, and in all probability not to be recovered. The general rule 
is, in the words of Horne Tooke : " Nothing in language is arbitrary or conven- 
tional." Language, like political constitutions and national character, is a growth, 



THE PHILOSOPHY OF LANGUAGE. 347 

not a convention or an institution. The most superficial dissection of the 
familiar forms of words, as we have them in our grammars, distinctly shows this. 
A mo amas means merely love I, love thou; the Sancrit asmi, the Latin sum, 
and the Greek dpi, being merely the two interflowing elements which are 
presented separately in the Gaelic tlta mi and the English / am. So the case 
terminations in Greek and Latin are merely significant attachments expressive 
of local relationship which have grown into the root in these terminational 
languages, but of which the meaning stands clear in that detached form 
which these agglutinated postpositives present as independent propositions ; 
the sign of the genitive in English of being manifestly = off, Greek cbrd, Latin ah, 
away from. It matters nothing that we cannot in all cases, or in the majority 
of cases, distinctly put our fingers on the original significant form of the abbre- 
viated or polished case termination ; enough that man is a reasonable animal, 
and that from his reasonable proceeding in known cases we can certainly divine 
it in where the formative action is hidden from our view. Words as we have 
them, especially terminations, conjunctions, and other such frequently used and 
much abused elements of the vocal currency of a country, are like old shillings 
from which the image and superscription has been defaced, but which certainly 
was there, as it lies in the very nature of a coinage to bear some stamp and 
authoritative signature on its face. 

VIII. That some modifications made in the root are without separate signi- 
ficance, and may without impropriety be called arbitrary and conventional, I 
think we must admit ; and so Horne Tooke's rule, like other rules, will have its 
exceptions, and must not be pressed urgently in all cases. Any child could tell 
how rubefacio signifies to make red ; it is merely two words run into one, in the 
same way that the Greek use woieco in aproTroios, a baker ; but no man can tell 
me how fell came to signify to cause to fall, or how the plural of man should 
be men. No doubt in this latter case you may say that the a of the singular 
was changed into the e of the plural by the reflex contagion of the e in the plural 
termination Manner ; but this is merely the description of a process of contagion 
or infection taking place between two contiguous emissions of articulated breath, 
not the laying bare of any natural significance in the change which has taken 
place. There is nothing in the word fell that should cause it to mean to cause 
to fall ; it is a pure matter of convention — an ingenious device, let us say, to 
make one word serve two purposes, as faces have been made by ingenious 
draughtsmen representing two different persons, according as you look at them 
from this side or from that. In the same way no conceivable reason can be 
given why ivilre in German, were in English, should be the subjunctive mood of 
was ; or, what is similar, why the a of the indicative of the Sanscrit or Greek 
should be softened into 77 in the subjunctive. It is for the sake of variety and 
distinction alone that such changes are made ; and they are in this view perfectly 



348 EMERITUS PROFESSOR J. S. BLACKIE ON 

analogous to the change of accent which takes place in English when a verb and 
a substantive are in all other respects identical, as in protest and protest, or in the 
rase of proper names in Greek — A loyevrjs. born of Jove ; A loyeVqs, a man's name ; 
Se£ dpevos, having received ; A ef aprnvos, Mr Receiver. A phenomenon somewhat 
different from these cases presents itself in the case of diminutives, which are 
made in most languages by the addition of terminations, which, though possessing 
no separate meaning in themselves, do really suggest the idea of littleness by the 
character of the differentiating syllables. Thus the terminal /, being a pleasant 
soft letter, and easy to dwell on prettily with a kindly tongue, seems to have 
been used in various languages to express diminutives — as in Latin puer, puella, 
puerulus ; German Mayd, madl ; Italian donna, donzella, dama, damigella. The 
same explanation may apply to the vowel p in the Greek 7rat,Sapi, from 7rcuS. 
It is impossible, however, to see the same propriety in the termination lo-kos 
used to diminish substantives in Greek, as ish is to diminish adjectives in 
English, and ike in Scotch, as in lass, lassie, lassikie. It is probable that all 
these terminations, as also the Greek ikos adjectival termination, are only 
varieties of the verb iiKO), to be like, in which case they belong not here, but to 
our previous section. 

IX. Before proceeding further, it may be well to make two remarks 
about roots. (1) However remote the single Sanscrit monosyllabic roots in dha, 
tha, ma, &c., may appear from any ejaculatory or mimetic origin, I most firmly 
believe that they are merely the curtailed forms of words which had such an 
origin, starting from the impressions made on the senses or from external 
sensations ; as, for instance, when Max Muller says that pate?; a father, 
comes from the root pa, to nourish — even if that be true — I am not at all sure 
that the root pa, to nourish, did not first come from the kindly babble of infantile 
lips which produced papa, mama, Amme, pcua, and Dt?. (2) All roots are, and 
must have been verbs originally, for the simple reason that substantives could 
not receive names except from certain qualities residing in them; but qualities, 
so long as they are quiescent, do not strike the senses sufficiently to stir the soul 
to that vocal utterance which is the word ; therefore adjectives, being quiescent 
qualities, could not be the first words, but verbs, which are energising qualities or 
functions. But the first word, though a verb, while the language-forming 
instinct is yet in its infancy, would answer all the three purposes of verb, sub- 
stantive, and adjective ; as happens in our bald and unterminational English 
every day— -fire, to fire, fireman — which, had the Englishman spoken Greek, 
would infallibly have assumed the triple form of nvp, -rrvpevo), and irvpevTri*;. 

X. Hitherto we have spoken of language only as a useful machinery for the 
purpose of communication among social creatures; but language is also a fine 
art, and that in a double sense : a fine art fashioned by Nature under the 
influence of that striving towards the Beautiful which is apparent in all the 



THE PHILOSOPHY OF LANGUAGE. 349 

Divine workmanship, and again cultured and improved by man in virtue of his 
divine origin and divine mission on earth, so beautifully expressed by the Stoics — 
Contemplari atque imitari mundum. Now, in this view, the perfection of a 
language will depend in the first place, as in a musical instrument, on the 
number and variety and completeness of the notes which it contains, and again 
on the quality of these tones, and lastly on the skill with which they are used by 
a natural genius and a practised player. With this high ideal before us, we 
shall certainly find no human language perfect ; for, besides that the organs of 
utterance in some cases may be of less perfect construction and of inferior 
capacity, the most highly gifted peoples in the use of language are apt to have 
pet tendencies and to fall into mannerisms, which are not only bad in them- 
selves, but do an additional harm by excluding other less-favoured elements of 
a perfect vocal gamut from fair exercise. Thus the language becomes lopsided, 
and, as in the case of a body palsied in one limb, presents an appearance of 
completeness which its power of action does not warrant. It appears to have 
two arms, but can strike only with the right or With the left. Any vital 
function rarely used is used with difficulty, which gradually hardens itself into 
an impossibility ; and so we find whole nations of the highest organic accom- 
plishment unable to pronounce certain letters ; as the Germans cannot pro- 
nounce th at all, and the English regularly change the x of the Greeks and the 
Scotch ch into k. Some nations cannot even distinguish r and I, both liquids, 
no doubt, and so akin, but considerably different, both in the movement of the 
tongue by which they are pronounced, and in their musical effect on the ear. 
On the other hand, the aspirate which the German cannot enunciate is so 
familiar to the Celt that he introduces it regularly where it does not belong, 
and not rarely allows it, as in the Gaelic ha for ta, to override and delete the 
consonant which it modifies. There is hardly a nation that does not get into a 
bad habit of using one part of the machinery by which vocal breath is emitted 
with such preference as to impart a mannerism so strong as to become a 
distinctive mark of nationality ; thus the Englishman, by the preferential use of 
the back of his mouth, gets into what is called the ha-ha style, and the curtailing 
of the r of its fair proportions, so that 

I saw 

A beautiful sta-aiv = star, 

is a perfectly good rhyme to a London, but not to an Edinburgh ear. The 
Greek, on the other hand, gave a preference to the front of the mouth, which 
produced the v^iXov and the ou = oo, which the Englishman in his ignorant 
i insular fashion refuses to recognise. The Yankee nasalism is another familiar 
j instance of the same kind ; and the vocalisation even of the liquid /, as 
in Versailles, of the modern French, is the most recent instance of the 



of>0 EMERITUS PROFESSOR J. S. BLAOKIE ON 

polished feebleness in which that emasculated offspring of the Latin language 
delights. 

XL The quality of the vowels, and the choice and combination of consonants 
by which the music of language is specially affected, must depend partly on the 
delicacy of the original senses and organic tissue ; and that this is influenced in 
a considerable degree by the climate, that is, by the atmosphere which the 
speaker breathes from his cradle, can scarcely be doubted. Hence the greater 
fulness and sweetness of the English vocalisation compared with the Scotch ; 
hence, perhaps, the less musical character of the Teutonic languages generally as 
compared with the Greek and Latin. But, though climate no doubt asserts its 
sway here, as in a matter as much physical as moral, national character, at the 
same time, as the moral element which affects enunciation, cannot fail to make 
itself felt; so the Germans and the Scotch, being a more emotional people than 
the English, put more soul into their syllables, and draw out their words with a 
more kindly moral emphasis ; and it seems impossible not to deduce the nos 
tamen sumus fortiores of Quinctilian, spoken in contrasting Latin with Greek, 
from the radically different character of the two peoples. But here we must 
remark, that the ideal of harmony in a language consists not merely in rich- 
ness and sweetness, but in that grand and curiously varied combination of 
strength and sweetness by which the great compositions of a Beethoven or a 
Handel distinguish themselves from a pleasant or a plaintive popular ditty. 
Now the strength or the bones of a language are in the consonants ; and the 
trunk, so to speak, of the word lies in the root ; so that the typical language is 
that which has always at hand a strong combination of consonants to express 
strong feelings, and a rich flow of vowels to express the more delicate emotions. 
Now, as we have already said, it is extremely difficult for a language to possess 
all excellences ; as the French avez for habetis, pere for the Italian padre, peat 
for potest, not to mention the systematic deletion of the nt in the final syllable 
of the present indicative of verbs, are a strong proof of how apt polish in this 
region is to degenerate into feebleness. Nay, it seems absolutely impossible, 
even in the best constituted languages, to combine sweetness with strength in 
the degree which an ideal type would demand ; for, as the most significant and 
dramatically most effective part of a word lies in the root, it follows that when- 
ever a strong utterance is to be fairly given, then the root which dramatically 
expresses the strong word ought to be made prominent. On the other hand, 
as the music of a language depends very much upon the cadence of the termina- 
tions, which in fact have only their vocalic element to recommend them, it 
follows that, whenever sweetness is to be expressed, these terminations ought 
not to be cheated of their natural emphasis. But, as a matter of fact, these 
terminations being affixed without distinction to all kind of roots, either, 
being accented, will swamp the root, or, being unaccented, will be apt to lose 



THE PHILOSOPHY OF LANGUAGE. 351 

part of their full musical value, or, at all events, prevent the root from standing 
so emphatically on its own legs, and producing its full dramatic effect. One 
line from Homer will show this — 

Bov7Tt](T€v Se Trefxoiv apafirjcre Be rev^e in olvto), 

and this may stand to verify the general proposition that the English language, 
besides being superior generally to either Greek or Latin in the dramatic truth 
and vigour of its roots, by virtue of its very lack of terminations, has a dramatic 
power in its daily use, which it is as impossible for Greek to emulate as it is 
impossible for English to emulate Greek in the volume of sentences and the 
cadence of periods. 

XII. In the music of language, as the vowels are more sonant than the conso- 
nants, so the long vowels and the broad vowels, as a and o and u, are more musical 
than the short vowels and the slender vowels. Next to the quantity or volume 
of sound, the pitch of sound, accompanied as it naturally is with an emphatic 
dominance of the accented syllable, has a notable effect on the music of spoken 
address, and cannot be transposed or neglected without doing violence to the 
genius of the language. In respect of accent, the Greek, as noted by the ancient 
rhetoricians, has a decided advantage over the Latin, in allowing the accent to 
ride freely, according to certain laws, over the three last syllables ; while the 
Latin, like the Gaelic, altogether excluded the accent from the last syllable of 
the word, where it is most musical. As the accent is one of the most character- 
istic, so it is one of the most persistent elements of the vocal life of a people ; and 
in the case of Greek is, accordingly, prominent alike in the books of the ancient 
grammarian and in the mouths of the modern people ; a fact which renders 
inexcusable the practice of English Hellenists in transferring wholesale the 
Roman system of accentuation to the Greek. We have no more right to tamper 
with the music of any language than with the colouring of a great painter or 
the diction of a great poet. 

XIII. A written alphabet, or a body of visible signs significant of sounds, is 
no doubt a grand invention, and a great convenience, but belongs to the philo- 
sophy of language only in a very indirect fashion. A written, graven, or 
printed language is for record primarily, not for expression ; like a photograph, 
it is an exact likeness, but without the expression which is the soul of the living 
image. An Orpheus, therefore, and a Homer, the highest form of lyrical and 
epic poetry, was possible to Greece, if not before a written alphabet was known, 
certainly before it was used for purposes of writing and reading. Neverthe- 
less, it seems certain that without the habit of writing and reading books, 
certain forms of literature which appeal to calm introspection, rather than to 
present excitement, could not have existed; without a written alphabet, Homer 

VOL. XXXII. PART II. 3 L 



352 EMERITUS PROFESSOR J. S. BLACK1E ON 

and JIesiod could never have been followed in due season by the large range of 
historical survey in Herodotus, and the condensed summation of political wisdom 
in Thucydides. A printed alphabet, therefore, we may say, is the mother of 
prose literature, and of the wide expansion of intellectual sympathy and linguis- 
tic expression which a prose literature implies. A people that does not read and 
write will never demand and never acquire any form of intelligent utterance 
beyond the historical ballad, enlarged, it may be, into the popular epic, the 
sacred hymn, the secular song, and the popular harangue. An example of this 
we have at our own door in the Highlands. The only other remark that occurs 
to me to make on the alphabet is, whether it ought to be a system of visible 
symbols distinctly representing articulate sounds, as in all the languages with 
which European civilisation is familiar, or indirectly by means of abbreviated 
pictures of the things which the words represent, as in the ideographic writing of 
the Chinese. This method, compared with the other, is evidently the product of 
an earlier stage of civilisation, crude, clumsy, and cumbrous, having neither the 
poetry of a picture, nor the flexibility of an alphabet of spoken signs to recom- 
mend it. But whether the use of it entails on the people who have not 
advanced beyond this first stage of visible speech, any other disadvantage than 
the necessity of cumbering the mind with a more complex array of memorial 
signs, I do not know, and shall be happy to learn.* 

XIV. Language, as noted above, is not a convention, but a growth ; and as 
a growth, like the human individual, has its infancy, its youth, its manhood, its 
age, its decrepitude, and its death ; and the same circumstances that favour or 
stunt the growth of the individual affect in a similar way the growth of a lan- 
guage. The best parentage for a language is a fine climate and a great story 
teller, in its infancy and youth. The Greeks had both. Homer was at once 
their secular and their sacred Bible ; and as such acted powerfully from the 
first, and without any diminution of action even to the present hour, both as a 
spur and a rein ; a spur to exertion so brilliantly begun, and a rein to unre- 
gulated, unchastened, and unfraternising exertions in future fields of intellectual 
glory. The next condition of the luxuriant growth of language — of course, 
always supposing rich natural endowments — is that the national mind, the 
outcome of the national life, should not be disturbed in the natural progress of 
its evolution. This disturbance usually occurs from some extraneous influence, 
acting either violently in the way of conquest, or peacefully in the voluntary sub- 
mission which a weak nation is always apt to pay to a stronger. From both 
these disturbing forces the Greek language remained free. Escaping trium- 
phantly by the heroic struggles of Marathon and Salamis from the threatened 

Since this paper was read I have seen Professor Legge of Cambridge, who expressed himself 
decidedly of opinion that the ideographic writing of the Chinese acts as a hindrance to the rich develop- 
ment of the spoken language. 




THE PHILOSOPHY OF LANGUAGE. 353 

despotism of Asia over Europe, Greece had full time to put forth her intellec- 
tual strength in all departments, according to the law of a natural growth, before, 
from internal dissensions, she was obliged to submit politically to the world-wide 
influence of Rome. But here again the importance of an early and ripe culture 
of the national language showed itself in the most brilliant style. The con- 
queror, instead of crushing, stooped to adopt the language of the conquered; 
and when the Western Empire fell to pieces by the incursion of northern 
barbarians, Greek still flourished in the oldest half of the Christian Church 
and the Eastern half of the Roman Empire. It thus obtained a lease of life 
more than 1000 years beyond what might have been supposed to be the epoch 
of its natural demise ; and when, by the overthrow of the Byzantine Empire in 
1453, its complete collapse seemed almost certain, the repulsion between the 
Turkish faith and the Christian preserved the language from the amalgamating 
and absorbing force which, under the common circumstances of conquest, must 
have worked its dissolution. It remains, therefore, at the present hour, a 
wonder of linguistic longevity unique in the history of language, and bidding 
fair, in spite of the artificial life in which Latin is preserved by the Roman 
Church, to spread out the branches of a green old age over every part of the world 
that is not too wise in its own conceit, or too isolated in its own narrowness, 
to own the civilising influence of the moral culture which belongs to the present, 
only when it bears with it the most valuable inheritance of the past. 

XV. The disturbing forces alluded to in the previous section either produce 
what may be called a violent death, if the resisting forces, as in the case of Gaul 
and Spain when conquered by Rome, are weak, or they produce a fusion more 
or less complete between the superimposed and the underlying stratum, and 
a mixed language of greater or less heterogeneousness of structure is produced. 
Such is the character of our own English tongue. Now, though it is quite sure 
that chance cannot make a language any more than a world, yet out of a chanceful 
throwing together of two languages, a mixed product of very excellent character 
may proceed ; just as when two good puddings are thrown together, the com- 
pound result will at all events contain all the good that is in each of the constitu- 
ents, a good resulting not from the chance fashion of the mixture, but from the 
cunning preparation of the materials out of which the mixture was made. With 
all this, however, it is quite certain that this blind way of throwing two good pud- 
dings into one is not the way to make the best pudding ; there is no certainty 
in such a process that the two puddings may harmonise and coalesce into a 
congruous, classical unity of the pudding genus. And so the English language, 
however excellent, and however worthy of the commendation of such a distin- 
guished philologer as Jacob Grimm, and however glorified by its having been 
made the organ of expression by the greatest dramatist the world ever saw, has 
some very manifest defects, which, both from a philological and a practical point 



354 EMERITUS PROFESSOR J. S. BLACKIE ON 

of view, place it on a lower platform than such self-developed languages as 
Greek and German. For (1) by the violent disturbance of its growth at an early 
period of its development, its power of compounding simple words and using its 
own roots has been so maimed and curtailed, that it is constantly obliged to borrow 
from all sources, in a fashion often clumsy and inelegant, and without that com- 
plete assimilation which is necessary to enable borrowed forms to satisfy the 
demands of a cultivated linguistic taste. (2) The linguistic instinct of the people 
acts so weakly that any irregularity creeps easily into it, and a subjection to the 
whims of fashion, that mar its aesthetic effect, and render it very difficult for a 
stranger to follow its vagaries. This remark applies particularly to the pronun- 
ciation and accentuation of our tongue. (3) What is worst of all, the immense 
mass of borrowed materials, taken and constantly being taken into our language 
from foreign sources, distinct both in space and time from our colloquial cur- 
rency, issues in the creation of a stratum of language, running parallel to the 
vulgar English, which only scholars and persons of large foreign culture can 
readily understand ; thus planting a prickly fence between the learned and the 
unlearned, in the highest degree unfavourable to the diffusion of scientific 
knowledge. It is an evil similar in kind, though less in degree, to that under 
which the whole of Europe suffered before the appearance of Dante in Italy, 
Shakespeare in England, and Lessing in Germany, viz., that, while social inter- 
course was carried on in the language of the country, knowledge of every kind 
was acquired and accumulated and stored in the language of the ancient Romans. 
XVI. But the phenomena caused by the violent invasion of one language 
by another are not exhausted either by the complete extinction of the invaded 
language on the one hand, or by its hybrid mixture with the invading language 
on the other. It is possible, on the one side, that the language of the invaders, 
though maintaining its acquired dominion, and remaining in all its constituent 
elements substantially the same, may, through tlie combined effects of time, 
change of atmosphere, and action of new circumstances, undergo such extensive 
modifications as to become, not a new language indeed to the eye of the philologer, 
but an old language with a new face ; and, on the other side, it is equally possible 
that the language of the invaded country, partly from its own inherited strength, 
partly from the intellectual weakness of the invader, may maintain its ground 
firmly, and yet, as in the previous case, from the influence of time and action of 
new social forces, become practically to the vulgar eye a new language, while 
to the scientific eye it is only a modification of the old. Of these two classes of 
what we may call, not mixed but metamorphic languages, the Romanesque 
languages — French, Spanish, Portuguese, and Italian — form familiar examples. 
To understand their formation we must bear in mind that, as all things in the 
world, specially all living things, in Heraclitus' phrase, pei irdvTa, are in a 
constant flux, so specially language, from being a very fluid material, and easily 




THE PHILOSOPHY OF LANGUAGE. 355 

yielding to slight and accidental influences, when it has once acquired a fixed and 
what may be called a classical type, can preserve this type only so long as the con- 
tinuity of political and intellectual forces to which it and the type belong is not 
broken. The moment this continuity is broken, which acts as a restraining and 
conservative authority, the loose elements of which every language is composed 
are set adrift, so to speak, and left to be affected in every possible way by incal- 
culable and often capricious forces, of which action, continued through genera- 
tions, a metamorphic type of the original tongue must necessarily be the out- 
come. The changes thus produced on the old classical type of the language 
may be classed partly under the head of what Max MOller calls phonetic 
decay; that is, a smoothing and rubbing down of the language, by a process 
similar to attrition in the mineralogical world — a process which is always in one 
sense a corruption, and which often arises from no nobler cause than the 
laziness or carelessness of the speaker, but which, in the result, according to the 
degree of its action and the character of the materials acted on, may either be an 
emasculated enfeeblement or a musical improvement of the original tongue. But 
these changes are not all processes of decay; along with the decay a process 
of reconstruction is largely going on, in which the most active element is the 
coming to the surface and emphatic self-assertion of certain original vital and 
plastic forces in the popular tongue, which had been over-ridden and suppressed 
so long as authority and fashion maintained the cultivated type of the language 
in a position of acknowledged superiority. Add to these elements a very 
slight sprinkling of strange elements in the metamorphic tongue — such as of 
Arabic in Spanish, of Teutonic in French and Italian — and we have dis- 
tinctly before us the conditions under which all metamorphic languages of 
the two classes represented by French and Italian assume their new type. Both 
languages are substantially Latin ; but in the one the invading element became 
subject to the metamorphic action from the downfall of the Roman Empire, and 
the loss of all linguistic guidance thereon consequent ; while in the latter 
the language of the invaded survived in a metamorphic shape, partly from the 
partial and irregular action of the invading powers, but principally from 
the ecclesiastical and intellectual supremacy which, under the most unfavourable 
circumstances, the invaded language did not fail to assert. It need scarcely be 
remarked also that, in proportion as the native Latin form of the language 
acted with more potency and with less disturbance on its native Italian ground 
than when transferred to Celtic France, in the same proportion, Italian would be 
a less corrupted, a more masculine, and a more majestic form of the old Roman 
tongue than that which is now wielded so dexterously by the brilliant wits and 
clever writers of the old insula Parisiorum. 

XVII. Under this section, which has led me to talk of phonetic decay, I may 
put a question which has often occurred to me, but to which I felt I had no 



356 EMERITUS PROFESSOR J. S. BLACKIE ON 

materials for supplying a satisfactory answer, viz., whether is the extremely 
vocalic structure, and the weakness of the consonantal element observable in 
the language of certain savage or semi-savage peoples, owing to the attrition of 
time, or to an original defect in the lingual organisation of the race ? 
Analogy leads to the former alternative ; but both answers are possible j and 
local record alone, in the form of old inscriptions, or translations by missionaries 
in early times, could supply materials for deciding definitely on one side rather 
than on the other. 

XVIII. The peaceful disturbance of the national process of growth, in any 
language, by the process of quiet decay and obliteration, takes place when a 
small people with an inferior literature finds itself in close geographical con- 
junction and in overpowering social connection with a people vastly superior in 
number, in wealth, in intelligence, in policy, and in every element that consti- 
tutes a highly developed social organism. In this case the language is doomed 
to a slow, it may be, but to a certain death ; for as certainly as coals will be 
imported from Newcastle or Fife or Mid-Lothian by those who have none in 
Ross-shire or Caithness, so certainly will English ideas and English speech 
penetrate into the remotest glens of the Celtic Highlands ; and though, as in 
Ireland, from obvious causes, the people may assert a distinct and well-marked 
nationality, the language in which their most cherished traditions have been 
handed down will not be able to maintain its ground. Not that there is any- 
thing desirable in the extinction of an old and venerable form of speech ; quite 
the contrary. Let dying languages be preserved with pious care by those who 
love them, and those to whom they belong ; there is no reason why we should 
kick our grandmother into her grave merely because she is old; let her tell her 
old stories and sing her old songs, nothing could be better — better even than 
sermons sometimes ; but however good they may be, they can serve only for 
our occasional recreation, not for our daily food. The Celtic languages in 
Europe, with the miraculous facility of communication now everywhere to be 
found, Avill certainly die out in a very few generations ; first in Ireland, strangely, 
where the Celtic blood is most hot; second, in the Scottish Highlands ; and, lastly, 
in Wales. The Scottish language, again, though daily dying out, even among 
the lowest classes, as a medium of social intercourse, has a better chance of sur- 
viving, in its lyrical Avatar, as the Doric dialect of the English, if only the 
Scottish people would be true to themselves, and not submit so tamely to the 
process of Anglification which, from obvious causes, is spreading so rapidly 
over the land. A very little decent attention to the national music in our 
highest as well as in our lowest schools would act powerfully in preserving in a 

n old age the most pleasant manifestation of our existence as a separate 
people ; but the mass of men in all countries are lazy and cowardly — ol 7ro\\ol 
kclkoI — and incline always to swim with the current rather than to ask whither 



THE PHILOSOPHY OF LANGUAGE. 357 

the current is driving them ; and in a town like Edinburgh, which, though metro- 
politan by public law and by historical tradition, must, since the Union, be more 
or less provincial in respect of London, there will always be in influential 
quarters a considerable majority of persons who, under the influence of aristo- 
cracy, plutocracy, bureauocracy, and other potent forces working from above, 
will prefer the meretricious glitter of borrowed accomplishments to the healthy 
glow of home-grown virtues. 



( 359 ) 



XXI. — The Old Red Sandstone Volcanic Rocks of Shetland. By B. N. Peach 
and J. Hokne, of the Geological Survey of Scotland. (Plates XLV. and 
XLVI.) 



CONTENTS, 



PAGE 

Introduction, 359 

I. Geological Structure op the Volcanic 

Rocks, 361 

A. Contemporaneous Lavas and Tuffs, . 361 

1. Porphyritic Lavas and Tuffs of North- 

mavine, . . . .361 

2. Diabase Lavas and Tuffs of Aithsting 

and Sandsting, .... 364 

3. Probable Horizon of the Lavas and 

Tuffs of Aithsting and Sandsting, 365 

4. Lava of the Holm of Melby, . . 366 

5. Bedded Lavas and Tuffs of Papa 

Stour, 366 



PAGB 

5. Necks on Bressay and Noss, . . 377 

6. Summary of Events indicated by 

Volcanic Phenomena of Shetland 

Old Red Sandstone, . . . 378 



6. Band of Tuff in Bressay, 
B. Intrusive Igneous Rocks, .... 

1. Intrusive Sheet of Binary Granite 

in Northmavine, .... 

2. Intrusive Sheet of Granite in Sand- 

sting, 370 

3. Intrusive Sheet of Spherulitic Fel- 

site in Papa Stour, 

4. Dykes — .... 

a. Binary Granites, 

b. Quartz-felsites, 

c. Rhyolites, 

d. Diabase Rocks, 



367 
368 

368 



371 
373 
373 
373 
374 
376 



II. Microscopic Characters. 



1. Porphyrite Lavas, 

2. Diabase Lavas, 

3. Intrusive Diabase 

Rocks, 

4. Intrusive Sheets — 

Rooeness Sheet, 
Sandsting Sheet, 
Papa Stour Sheet, 

5. Dykes — 

Binary Granites 
and Quartz-fel- 
sites, 

Rhyolites, 



Basic Rocks, 



Acidic Rocks, 



379 
379 

381 
382 
382 
382 
383 
383 

383 

384 



Summary of Results, 386 

Appendix. — Table of Chemical Analyses of 
eight Specimens of Shetland Old Red 
Volcanic Rocks, by R. R. Tatlock, 
F.R.S.E., 387 



Perhaps the most interesting feature connected with the Old Red Sandstone 
formation in Shetland is the evidence of prolonged volcanic activity in those 
northern isles. The great development of contemporaneous and intrusive 
igneous rocks, which gives rise to some of the most striking scenery in Shet- 
land, is all the more important when compared with the meagre records in the 
Lower Old Red Sandstone of Orkney and the Moray Firth basin. Not till we 
pass to the south of the Grampians do we find evidence of a far grander 
display of volcanic action during this period, in the sheets of lava and tuff in 
the Sidlaws and Ochils and in the great belt stretching from the Pentlands 
south-westwards into Ayrshire. The relations of the Shetland igneous rocks 
are admirably displayed in the various coast sections, especially in the mural 
cliffs of Northmavine and some of the Western Islands. From these records, 
though they have been subjected to much denudation, it is possible to con- 
struct a tolerably complete sketch of the volcanic history of this formation, as 
developed in that region. 

VOL. XXXII. PART II. 3 M 



300 B. N. PEACH AND J. HORNE ON THE 

No previous attempt has been made to furnish a chronological account 
of the Old Red volcanic phenomena of those northern isles. In Hibbert's 
admirable volume "" there are various references to the granite masses of the 
Mainland and the amygdaloidal claystones in the south-west of Northmavine. 
He also refers to the porjDhyritic and amygdaloidal rocks in Papa Stour, which 
were likewise described by Dr Fleming^ In various papers published in the 
Mineralogical Magazine,\ Dr Heddle notes the existence of interbedded and 
intrusive igneous rocks of this age in Shetland, with descriptions of the minerals 
obtained from them. The first attempt, however, to connect these Old Red 
volcanic rocks with their representatives south of the Grampians, was made by 
Dr Archibald Geikie, the present Director-General of the Geological Surveys. 
In 1876 the geological structure of Papa Stour, which is almost wholly com- 
posed of volcanic rocks, was solved by him in company with Mr B. N. Peach '> 
and, as the result of that traverse, an account of the geology of that interesting- 
island was given in his celebrated paper on " The Old Red Sandstone of 
Western Europe," published in the Transactions of this Society. § Though 
unable to visit the volcanic rocks on the north side of St Magnus Bay, he 
ventured to suggest that^ the amygdaloidal claystones referred to by Hibbert 
would turn out to be merely a repetition of those in Papa Stour, — a suggestion 
which has been amply verified by subsequent investigations. 

During our successive visits to Shetland, which were undertaken mainly 
with the view of examining the glacial phenomena of the group, we were 
induced to pay close attention to the distribution and geological structure of 
the Old Red Sandstone rocks, on account of the important bearing which they 
have on the ice-carry during the glacial period. A brief sketch of the develop- 
ment of the contemporaneous and intrusive igneous rocks was given in the 
paper which we communicated to the Geological Society in 1879. || But since 
that paper was read we have twice visited the is